Unsolved Mysteries About the Planet Earth
♦ Mystery 1: Where did all the water come from?
Water covers 70 percent of Earth’s surface and earns it the nickname “the blue planet”. But where did it come from? The most popular scientific theory states that the H2O came from several violent asteroids (小行星) filled with ice. Another suggests that the water actually has been around since Earth’s formation. However it happened, though, it’s certainly worked out well for Earth’s life forms.
♦ Mystery 2: What about all the oxygen?
Another thing is the planet’s oxygen. Tiny creatures released oxygen as a waste product, filling the atmosphere with it. After that, the level of oxygen in Earth’s atmosphere went wildly up and down until it finally calmed down around 540 million years ago. Since then, it’s remained at about the breathable level we experience today. But what caused it to be suddenly steady?
♦ Mystery 3: What caused the Cambrian (寒武纪) Explosion?
The Cambrian Explosion refers to the explosion of complex life forms that occurred on Earth about 540 million years ago. Before then, life had consisted mostly of bacteria. But at the beginning of the Cambrian period, complex creatures began developing at a rate never seen before. Suddenly, life forms had brains, eyes, and bones. Most living creatures today can trace their blood back to the Cambrian period.
♦ Mystery 4: Will we ever be able to predict earthquakes?
We still haven’t been able to come up with a way to accurately predict earthquakes. We can certainly try, but our current technology cannot predict them exactly. We know that earthquakes start when rocks crack underground and send earthquake waves toward the surface, but we haven’t figured out why that happens, or how to predict it.
1. What was created later by creatures on Earth?| A．Oxygen. | B．Water. | C．Bacteria. | D．Ice. |
| A．Earth is called the blue star because of water coverage. |
| B．The level of oxygen has been steady all the time. |
| C．Complex creatures had rapid development in the Cambrian period. |
| D．We know nothing about predicting earthquakes. |
| A．It is the oldest mystery of the four. |
| B．It will be solved in the near future. |
| C．It is the most difficult mystery to solve of the four. |
| D．It is a matter that has extremely practical significance. |
相似题推荐
【推荐1】A new study of older adults finds too much daytime napping (小睡) may signal an increasing risk of Alzheimer’s disease. Investigators from Brigham report a relationship between daytime napping and cognitive (认知的) aging: too much daytime napping predicts an increased future risk of Alzheimer’s, and Alzheimer’s speeds up the increase in daytime napping during aging.
“Daytime sleep behaviors of older adults are often ignored, and an agreement for daytime napping in clinical practice and health care is still lacking,” said Peng Li of the Medical Program in Brigham, “Our team calls for a closer attention to 24-hour sleep patterns — not only nighttime sleep but also daytime sleep—for tracking the health of older adults.”
Researchers at the Brigham recognized that all previous studies on Alzheimer’s disease assessed napping within a participant only once, and most of the studies were subjective and questionnaire-based. In the new study, more individuals, with an average age of 81, were involved. They were provided with Actical, a watch-like device, to wear on their wrist for up to 14 days. After napping periods were identified, the nap duration and frequency were calculated.
The results suggested that too much daytime napping may signal an increasing risk of Alzheimer’s, and that faster yearly increase in daytime napping may be a worsening sign of the disease.
Researchers acknowledge that although the method of the new study has been widely used in sleep field studies, they recognize that Polysomnography (多导睡眠记录仪) is the gold standard for sleep scoring. Moreover, the participants studied are older, and therefore, the findings may not be easily translated to younger people. In addition, future studies should test whether a direct intervention in daytime napping can lower the risk of Alzheimer’s or cognitive decline.
“We hope to draw more attention to daytime sleep patterns,” said co-senior author Kun Hu of the Medical Program. “Sleep changes are critical in shaping the internal changes in the brain.”
1. What is the possible relationship between daytime napping and Alzheimer’s disease?| A．More daytime napping causes Alzheimer’s disease. |
| B．Alzheimer’s disease can be prevented by more daytime napping. |
| C．Alzheimer’s disease decreases the time spent on daytime napping. |
| D．More daytime napping indicates a higher risk of Alzheimer’s disease. |
| A．The sample size was larger. |
| B．It only recorded the daytime napping. |
| C．The study was based on questionnaires. |
| D．Its findings can be applied to younger generations. |
| A．The patterns of nighttime sleep. |
| B．The symptoms of Alzheimer’s disease. |
| C．The application of the new study method. |
| D．The effect of an intervention in daytime napping. |
| A．Alzheimer’s: a Sign of Aging |
| B．Actical: a Device of Recording Napping |
| C．Closely Linked: Daytime Napping and Alzheimer’s |
| D．Slightly Different: Daytime Sleep and Nighttime Sleep |
【推荐2】Some animals see differently than we do.Some animals,like bees, have cones (视锥细胞) for colours we can’t see. Some animals have developed a highly-advanced senses of smell or hearing abilities.
The most interesting feature of night animals is the size of their eyes.
Although night animals see mostly imperfect shapes, outlines and no colours, by maximizing their sensitivity to low light levels with the above adaptations, it is enough for them to hunt, feed and survive in the dark of night.
| A．Others see things clearly at night. |
| B．Their large eyes can collect more light. |
| C．Instead,they have special ability in the neck. |
| D．It allows the head and eyes to remain motionless. |
| E．Some animals of the night have got a spherical (球形的) lens. |
| F．As this light is reflected off the tapetum,they appear to glow. |
| G．On a dark night, flash a bright light at your dog’s eyes and you notice that their eyes glow in the dark. |
【推荐3】Although midnight snacks or being too tired to exercise could make people get fatter,there may now be a more scientific reason. A study has shown short or restless sleep changes the way people’s DNA works and makes the body store fat. Fat stores begin to rise when people lose as little as one night’s sleep, the researchers found.
Sleep researchers from Uppsala University in Sweden did a study on people after two lab tests — in one they slept for over eight hours and in the other they did not sleep at all. Researchers then examined the make-up of fat and muscle tissue (肌肉组织), as well as measuring sugar levels in the blood.
The researchers found after just one night of sleeplessness, the body began to store more fat and to lose muscle strength. The body’s decision to store more fat when a person is tired appears to be related to a break in the body clock. When sleep times are changed, it disrupts (扰乱) the way DNA is used by the body and changes which processes are seen as most important, the scientists say. Sleep loss was already known to contribute to overweight but the scientists say they are the first to ever notice the physical changes that lead to putting on weight.
“We saw that the tissue is attempting to increase its ability to store fat following sleep loss,” said study author Jenathan Cedernaes. “We observed signs of breakdown of muscle. We also noted changes in the levels of proteins (蛋白质) related to dealing with blood sugar and this could help explain why the people’s sugar sensitivity (敏感度) was damaged following sleep loss. Taken together,these observations may partially explain why long-term sleep loss can increase the risk of putting on weight as well as the risk of serious diseases.”
The researchers say their findings are important because high levels of body fat increase the risk of the world’s biggest causes of death: cancer and heart disease.
1. What does the second paragraph show?| A．The background of the study. |
| B．The reasons for the study. |
| C．The process of the study. |
| D．The methods of the study. |
| A．It is the first of its kind. |
| B．It discovered something new. |
| C．It will encourage more related research. |
| D．It will last for a long time. |
| A．Heart disease is caused by poor sleep. |
| B．More and more people are short of sleep. |
| C．Overwork prevents people from sleeping well. |
| D．Sleep loss makes people less sensitive to blood sugar. |
| A．The importance of a good night’s sleep. |
| B．Poor sleep makes people fat and weak |
| C．The factors that affect the way DNA works. |
| D．The body clock plays a role in sleep management |
【推荐1】The local transport in Liverpool City Region is convenient for visitors to go around. The following are some means of transport for you to choose from.
By Train
Merseyrail trains run frequently throughout the day across 68 stations in and around the Liverpool area. With 4 city centre underground stations, you can easily get around the city.
You can now buy tickets online. Your ticket will be emailed straight to you, so you don’t have to think about it at the station, just jump on the train and enjoy your journey!
By Bike
Liverpool is easy to get around by bike. Bike parking can be found on the Liverpool Cycle Map. If you`re arriving in Liverpool by train or ferry (渡船), bikes go free.
The CityBike bicycle hire system is also available in the city centre. Find more information at www.citybiheliverpool.co.uk.
By Bus
Bus travel in and around Liverpool is a green and convenient way to explore the destination (目的地). The bus network is run by Merseytravel, with two main city centre bus terminals (终点站) — Liverpool ONE and Queen Square.
1. How many stations do Merseyrail trains run across?| A．2. | B．4. | C．64. | D．68. |
| A．At the bus station. | B．At the ticket office. |
| C．On the Liverpool Cycle Map. | D．At the underground station. |
| A．The City Bike | B．Merseytravel | C．Liverpool ONE | D．Queen Square |
| A．Visitors in Liverpool. | B．Life in Liverpool. |
| C．Travel transport in Liverpool. | D．Fun activities in Liverpool. |
| A．A science textbook. | B．A history magazine. | C．A travel guide. | D．A news report. |
【推荐2】Our Favourite Tech Gifts of 2019
When it comes time for the holiday shopping season, we’re extra choosy about the countless technology products that we will buy and give to friends and family. Here’s what impressed editors, reporters and producers the most in 2019.
Lumos Matrix helmet
I recently bought a Lumos Matrix helmet(头盔)(﹩229)with built-in lights to make riding my bike at night a lot safer and less stressful. It’s a regular pain point for bikers like me to make sure careless drivers see you, especially when it’s dark. This does help.
-Matt Mcfarland, Writer
Goodreads app
Although this isn’t a gift, the free Goodreads app is a game changer. At the beginning of 2019, I promised myself I’d read at least one new book every month. I set a goal of 12 books on Goodreads and use it to track my progress, keep a list of books I’m interested in and check out what friends and others on the app were recommending. I read 35 books this year! (That’s up from five books last year.) Goodreads feels like one of the rare feel-good social networks.
-Kaya Yurieff, Tech Reporter
Ember coffee cup
I drink my coffee slowly, so it has routinely cooled by the time I get halfway through it. For my birthday, my mum bought me a cup (﹩99), which keeps my coffee warm until I finish it without reheating. I can also set the temperature I want. It makes my mornings so much easier.
-Millie Dent, Intern
1. What is the main advantage of Lumos Matrix helmet?| A．Helping drivers concentrate. | B．Managing the bad weather. |
| C．Making night riding safer. | D．Making bikers less painful. |
| A．It changes some readers’ reading rules. |
| B．It inspires readers to read more through communication. |
| C．It limits the number of books a reader can read. |
| D．It provides readers with free Internet games. |
| A．Simple. | B．Expensive. | C．Eco-friendly. | D．Convenient |
【推荐3】Museum of International Cultures
A Center for Global Awareness and Understanding
International Film Series
The International Film Series is a year-long celebration of various cultures.
The series is held on the 4th Saturday of a month, alternating with the Cultural Dinner & Lecture Series every other month.
Both the film series and cultural dinner and lecture series begin at 7:00 p.m.
The International Film Series is hosted by Anne & Tim Perry.
Cost is Free.
CEF Workshop
The Chemical Education Foundation (CEF) is a professional development workshop designed to provide educators with methods for teaching chemistry concepts through hands-on learning and real-world connections.
To register for the free workshop, please send email to penny@acm.org with the following information: your name, your email address and telephone number, your school or group and its address, the grade levels you teach.
This free workshop for educators will be held on Saturday January 20, 2020. Sign-in starts at 9:30 a.m. and the workshop will run from 10:00 a.m. to noon.
Recharge Conference
This is a rolling one-day conference featuring community experts sharing information on health, finances, education, cooking, exercise tips, self-development, manhood, marriage and job searches.
Speakers include:
Clarence Davis, Opening Message on Connection;
Tonya Brown, “Trickeration 101,” with a message of strength and hope;
Darren Murphy, “Bug Straight Talk,” on overcoming addiction and restart new life;
Quinecka Ragsdale, “Demarcus Jones and The Solar Calendar,” on time travel and African/African American history;
Pastor Barry Jerking, “On The Road to Glory,” finding your life’s purpose as a man in society;
Oscar Ellis, on financing your business.
Cost is $10 in advance; $15 at the door, plus applicable fees.
1. How many times will the International Film Series be held in a year?| A．Twice. | B．3 times. | C．6 times. | D．12 times. |
| A．Young students. | B．Chemistry teachers. |
| C．Chemical scientists. | D．Industry workers. |
| A．Tonya Brown’s. | B．Darren Murphy’s. |
| C．Quinecka Ragsdale’s. | D．Pastor Barry Jerking’s. |
【推荐1】Hidden in the mountains of Jordan is the beautiful ancient city of Petra. It lay in ruins for more than a thousand years.
Petra was built in 312 BC by the Nabataeans who were an ancient southern Arab people. They were very skilled at carving(刻). It is no wonder that this ancient city has so much to offer!
In 363 AD, the city suffered from terrible earthquakes that left most of the city damaged. The buildings and the city’s water system were affected. A Swiss explorer, Johann Ludwig Burckhardt, discovered this city of wonders in 1812. Until he discovered Petra, it had been unheard of in the Western world for about 5 centuries!
Petra is the Greek word for stone and this name makes perfect sense because of where the city is located and how some of it is carved into the rock. The ancient city of Petra is also known as the “Rose City”. This is because the rock in which the city is built is a rosered colour. Many of the buildings of Petra have beautiful facades(正面). Some of the facades have columns(柱) carved into the rock, but they are for decoration and they don’t actually hold anything up.
Petra was built in the middle of the desert, where it hardly ever rained. Luckily, the Nabataeans were very skilled engineers and knew how to live in a hot and dry place. First, they carved channels(渠) to bring water from a nearby spring into the city. Rainwater was also collected in underground channels. The water was then stored. So, even in the long dry months there was enough water for people to use.
Today, Petra is one of the world’s most famous ancient sites and people come from all over the world to visit it.
1. What do we know about Petra?| A．It was built on high mountains. | B．It was a history of five centuries. |
| C．It was destroyed by earthquakes. | D．It was first visited by westerners in 363. |
| A．Some of it looked rosered. | B．Some of it was filled with roses. |
| C．Some of it was home to animals. | D．Some of it was built into the rock. |
| A．To beautify the buildings. | B．To support the buildings. |
| C．To function as gates. | D．To serve as tools. |
| A．Honest. | B．Creative. | C．Hardworking. | D．Welleducated. |
The Chicago Public Library (CPL) encourages lifelong learning by welcoming all people and offering equal access to information, entertainment and knowledge through materials, programs and events. Each year, Chicago Public Library recommends the Best of the Best, CPL’s selections of the very best books published that year.
● Hours
Monday: 10:00 am – 6:00 pm
Tuesday: 12:00 pm – 8:00 pm
Wednesday: 10:00 am – 6:00 pm
Thursday: 12:00 pm – 8:00 pm
Friday: 9:00 am – 5:00 pm
Saturday: 9:00 am – 5:00 pm
Sunday: Closed
● Holidays & Closures
All Staff Institute Day: Thursday, April 30, 2020 Closed All Day
Memorial Day: Monday, May 25, 2020 Closed All Day
Independence Day: Saturday, July 4, 2020 Closed All Day
Labor Day: Monday, September 7, 2020 Closed All Day
Thanksgiving: Thursday, November 26, 2020 Closed All Day
Christmas: Friday, December 25, 2020 Closed All Day
● Address & Contact
1625 W. Chicago Avenue Chicago IL 60622
Phone: (312) 743-0450
Email: westtownchipublib.org
● Get a Library Card
Getting a library card is easy – and it’s free! Please visit any CPL location to fill out an application.
Current, valid ID with name, photo and Chicago address is required.
● Facilities
After-hours book return Bike rack
Computers Meeting room Wi-Fi Parking lot Scanner
● Upcoming Events at West Town
Design Challenge Day
Description: Are you up for a challenge? Drop in and tackle some design challenges using supplies provided by the library. Prizes will be awarded for the most creative submissions.
Suitable for: Kids and Teens
Time: Tuesday, March 24, 2020, 5:00 pm – 6:00 pm
Film Screening: The Zookeeper’s Wife (2017)
Description: Join the West Town branch for a screening of The Zookeeper’s Wife. A married couple who work as zoo caretakers help save Jewish people from the Nazi’s Holocaust.
Suitable for: Adults and Teens
Time: Tuesday, March 31, 2020, 5:30 pm – 7:30 pm
1. When can people go and read in Chicago Public Library?| A．11:00 am, April 29, 2020. | B．2:00 pm, May 25, 2020. |
| C．9:00 am, July 5, 2020. | D．6:00 pm, November 26, 2020. |
| A．Paying for it in your free time on a yearly basis. |
| B．Providing a recent photo and an application. |
| C．Applying on the library’s official website first. |
| D．Having a valid ID with name, photo and Chicago address. |
| A．It targets adults as their major participants. |
| B．Participants will compete for prizes. |
| C．The activity will last for nearly 2 hours. |
| D．Winners can watch The Zookeeper’s Wife for free. |
【推荐3】Killer whales, or orcas, are known for their severe attacks on sea animals but they have never posed a threat to humans. However, since late July, the normally social animals have been intentionally attacking sailboats off the coasts of Spain and Portugal.
The strange behavior first surfaced on July 29, 2020, when a 46-foot boat was repeatedly attacked for almost an hour by nine orcas, causing the boat to rotate(旋转) 180 degrees and having its engine switched off. Since then, over 30 more similar incidents have been reported. On September 23, 2020, Spain's government banned boats of less than 50 feet in length from sailing in the 60-mile stretch of the Atlantic coastline between Ferrol and the Estaca de Bares Cape, where the attacks have been occurring.
Researchers across the world are trying to explain the orcas' behavior. Some believe it could be a result of the overfishing of the bluefish tuna - the orcas' primary food source -which has left the area's killer whales starving and unable to feed their babies. "I saw them look at boats carrying fish. I think they know humans are somehow related to food shortages, "says Ken Balcomb, senior scientist at the Center for Whale Research in Washington, USA. The environmentalists believe the sudden increase in boat traffic and fishing activities, after months of absence due to restrictions on human activity last spring, could also be contributing to the agitation.
However, Alfredo López, a biology professor in Galicia, Spain, thinks the attacks are defensive measures the orcas adopted to protect themselves against boat injuries. The researcher came to this conclusion after looking at the of the videos of a few incidents and noticing that two of the young killer whales involved had serious injuries. Hopefully, the experts will be able to find a way to restore the harmony between the animals and the humans soon.
1. What do we know about orcas in paragraph 1?| A．They are friendly to humans. | B．They have changed their behavior. |
| C．They are famous for hunting skills | D．They have met tough living conditions. |
| A．Ken Balcomb. | B．The environmentalists. |
| C．Alfredo López. | D．Spain's government. |
| A．The attacks. | B．Food shortages. | C．The overfishing. | D．Human activities. |
| A．How do killer whales attack humans? |
| B．Why Are Killer Whales attacking Boats? |
| C．How can we live in harmony with animals? |
| D．Why are boats banned from sailing on the sea? |
The event was swimming and started with only three men on the blocks. For one reason or another, two of them false started, so they were disqualified. That left only one to compete. It would have been difficult enough, not having anyone to race against, even though the time on the clock is important.
I watched the man dive off the block and knew right away that something was wrong. I’m not an expert swimmer, but I can tell a good dive from a poor one, and this was not exactly medal quality. When he resurfaced, it was evident that the man was not out for gold – his arms were waving in an attempt at freestyle. The crowd started to laugh. Clearly this man was not a medal competitor.
I listened to the crowd begin to laugh at this poor man who was clearly having a hard time. Finally he made his turn to start back. It was pitiful. He made a few desperate strokes and you could tell he was worn out.
But in those few awful strokes, the crowd had changed.
No longer were they laughing, but beginning to cheer. Some even began to stand and shout “Come on, you can do it!” and he did.
A clear minute past the average swimmer, this young man finally finished his race. The crowd went wild. You would have thought that he had won the gold, and he should have. Even though he recorded one of the slowest times in Olympic history, this man gave more heart than any of the other competitors.
Just a short year ago, he had never even swum, let alone race. His country had been invited to Sydney.
In a competition where athletes remove their silver medals feeling they have somehow been cheated out of gold, or when they act so proudly in front of their competitors ,
1. From the passage we can learn that the young man .
| A．made his turn to start back pitifully |
| B．was skillful in freestyle in the game |
| C．swam faster than the average swimmer |
| D．was not capable enough to win the medal |
| A．they felt sorry for the young man |
| B．they were moved by the young man’s courage |
| C．they wanted to show their sympathy |
| D．they meant to please the young man |
| A．it’s amazing to watch an ordinary man challenging himself |
| B．it’s amusing to watch a man with awful swimming skills |
| C．it’s cheerful for athletes to act proudly before their competitors |
| D．it’s brave enough for some athletes to remove the silver medals |
| A．The event started with three men, two of whom were disqualified later. |
| B．The crowd started to laugh at the athlete’s arms waving in an attempt at freestyle. |
| C．The athlete, as well as the author, is an expert swimmer. |
| D．The swimming event is a show of courage rather than a fierce competition. |
| A．Compete for Gold! | B．Try again! |
| C．Break a Record! | D．Go for it! |
【推荐2】In 2018 measles ( 麻疹) infected almost 10 million people around the world and killed 420. Countries that achieved high vaccination（苗接种） rates or had formerly eradicated the disease also failed to have narrow escape .
Fortunately, apart from troublesome measles, many inspirational global health stories happened in the last decade, new viruses, vaccines, and treatments were discovered, once again showing the significance of science.
Huge progress was made in virus research. For instance, a kind of virus named Medusavirus, which can turn an amoeba, a kind of single-celled living creature, into a "stone", was identified by Japanese scientists. The virus has one of the largest and most complicated viral genomes(基因组) that have ever been found. Besides, a new virus, Alongshan virus, was discovered in a group of patients in Inner Mongolia. Researchers also found for the first time that an insect RNA virus, the Providence virus, was able to infect plants and mammalian cells, which indicated that plants could serve as hosts of human viruses.
We also saw improvement in treatments and vaccines. Ebola virus is good case in point. According to the Royal Free Hospital in Britain, the drug MIL77, which had been developed by Academy of Military Medical Sciences, an institution in China, jointly with some other companies, was adopted to treat a Briton infected with the disease and helped her recover from the deadly virus. This has indicated China's capability of offering an economical and practical drug fighting Ebola virus worldwide. Furthermore, the Chinese and British medical research teams have worked on genome sequencing of the virus, making it possible to develop drugs and vaccines that are more effective. Therefore, Ebola is no longer a death sentence.
Thanks to investment in global supervision transnational partnership, and scientific research, many new viruses, vaccines, and treatments were successfully discovered in the last decade. But the journey will continue and much more needs to be done. For example, we need to have a deeper understanding of bow climate change influences the spread of infectious diseases
1. What does the underlined word "eradicated” in Paragraph 1 probably mean?| A．Got rid of. | B．Conducted research on | C．Lost control of | D．Come down with. |
| A．It is a newly identified virus . | B．It has the largest viral genome |
| C．It was discovered in Inner Mongolia. | D．It can infect both plants and humas |
| A．MIL77 is an effective Ebola vaccine. |
| B．No death will be caused by Ebola virus anymore. |
| C．China has made great contributions to fighting Ebola virus. |
| D．Genome sequencing of Ebola virus is too complicated to he carried out. |
| A．Science keeps improving global health | B．A victory over deadly diseases |
| C．Global cooperation in fighting viruses | D．Serious global health problems |
【推荐3】Many of us have wondered what Earth is like beneath the surface. So have writers and scientists. In French novelist Jules Verne's masterpiece Journey to the Center of the Earth, explorers go down to Earth's center and discover amazing wonders.
But in real life, human beings haven't even come close to the planet’s core (核心). The core is over 6,000 km down. The deepest hole ever created, according to the BBC, is the Kola Superdeep Borehole in Russia, which only goes 12.3 km down.
So how do we know about everything down. below without any samples? One good way to start is to think about the Earth's density, Simon Redfern of the University of Cambridge in the UK told the BBC. ''The density of the material on Earth's surface is much lower than the average density of the whole Earth, so that tells us there's something that has greater density, '' Redfern said.
The challenge is to find out which heavy materials the core is made of. And the main material scientists have found is iron. The idea is that when Earth formed 4.5 billion years ago, a lot of iron made its way down to the core, taking up about 80 percent of it. Today scientists are still working on finding out which other materials the core could be made up of.
You might also wonder how we know the size of the core. There's a one-word answer: seismology (地震学). When an earthquake happens, seismic stations around the world record the shockwaves it. sends throughout the planet. It's like hitting one side of the planet with a huge hammer and listening on the other side for the noise.
Early research found that some shockwaves, called S-waves, went missing. S-waves can only travel through solid material, but not through liquid, so they must have found something molten in Earth's center. By following the S-waves paths, scientists found out that rocks became liquid around 3,000 km down.
There are still many questions about Earth's core to answer. But the study of the dark world below isn't just for scientists' curiosity. The movement of Earth’s molten iron core builds up a powerful magnetic field. It protects us from radiation from the sun and is needed for compasses and GPS systems to work.
So perhaps none of us will ever set eyes on the core, but it's good to know it's there.
1. The author mentions Jules Verne's novel Journey to the Center of the Earth in the first paragraph to ________.| A．discuss the possibility of going down to Earth's center |
| B．show how much humans have discovered about Earth |
| C．paint a picture in our imagination of the dark world below |
| D．show humans deep interest in Earth's center |
| A．Earth’s center is completely made up of iron. |
| B．Scientists have found samples of Earth's core from the Kola Superdeep Borehole. |
| C．Scientists have no idea when and how iron made its way down to Earth’s core. |
| D．Earth has a higher density at its core than on its surface. |
| A．are often used to predict' earthquakes | B．cannot travel through liquid material |
| C．are the most noticeable shockwaves produced by earthquakes | D．can travel most rapidly at 3 ,000 kilometers below Earth's surface |
| A．research into Earth's core has hardly made any progress in recent years |
| B．improvements in GPS systems could help people find out more about Earth |
| C．Earth's core helps to protect humans from harm |
| D．scientists are likely to reach Earth's center within dozens of years |
