Radiation is the greatest known danger to explorers in space, The unit of radiation is called “rem” Scientists have reason to think that a man can put up with far more radiation than 0.1rem without being damaged; the figure of 60 rems has been agreed on. The trouble is that it is extremely difficult to be sure about radiation damage. A person may feel perfectly well, but the cells of his or her sex organs may be damaged, and this will not be discovered until the birth of deformed children or even grandchildren. Missions of the Apollo flights have had to cross belts of high radiation and , during the outward and return journeys, the Apollo crew accumulated(积累) a large amount of rems. So far, no dangerous amounts of radiation have been reported, but the Apollo missions have been quite short. We simply do not know yet how men are going to get on when they spend weeks and months outside the protection of the atmosphere, working in a space laboratory. Drugs might help to decrease the damage done by radiation, but no really effective ones have been found so far.
1. In which way is the atmosphere necessary to man according to the first paragraph?
| A．It screens off the falling meteors. |
| B．It provides enough light for plants to grow. |
| C．It supplies the heat necessary for human survival. |
| D．It protects him against the harmful rays from space. |
| A．exposure to even tiny amount of radiation is fatal( 致命的) |
| B．the effect of exposure to radiation is slow in coming |
| C．radiation is avoidable in space exploration |
| D．astronauts in spacesuits needn’t worry about radiation damage |
| A．badly-shaped | B．weak |
| C．naturally-grown | D．ugly |
| A．the Apollo mission was very successful |
| B．astronauts will have deformed children or grandchildren |
| C．protection from space radiation is no easy job |
| D．radiation is not a threat to well-protected space explorers |
相似题推荐
【推荐1】We humans are sweet on sugar. That makes sense. All animals need sugar to live. It ' s the fuel that powers our cells. So it' s not surprising that we ' re born to want the sweet stuff.
Sugar stores the sun' s energy like a battery. After a meal,your body breaks down foods into their building blocks. It uses some sugars for energy right away. The rest get stored for the body to break down later. It ' s a myth that sugar makes you extremely excited, but having a sugary snack can give you a quick burst of energy. That ' s because the sugars in sweet foods are easy for your body to turn into fuel. When you eat other kinds of foods,like vegetables, it takes longer for your body to break the sugars down.
These days it' s easy to find sweet snacks. Sodas, candy, cakes and even foods that seem healthy , such as yogurt,can be packed with sugar. Food makers add sugar,because they know that to humans, sweet makes everything taste better. Americans eat about 20 teaspoons of extra sugar everyday. That' s way more than what is good for us.
Eating too much sugar can cause more than a stomach-ache. It can make people overweight, decay the teeth and even cause diabetes. However, experts aren ' t worried about naturally sweet foods- the problem is added sugar. So go ahead and enjoy a sweet apple or even a sugar-rich carrot that are also full of vitamins and other good stuff.
Even cake is great once in a while , as long as you don ' t overdo it. After all, no one wants life to be dull. And your body needs its fuel!
1. The first two paragraphs are mainly developed by _'| A．cause and effect. | B．problem and solution. |
| C．giving examples . | D．making comparisons. |
| A．no one wants life to be boring. |
| B．we ' re born to want the sweet stuff. |
| C．so-called healthy food can be packed with sugar. |
| D．sugar is the fuel for the plants and animals on the Earth. |
| A．We' d better say no to sweet foods. |
| B．Experts are worried about added sugar. |
| C．Eating too much sugar is bad for our health. |
| D．We ' d better consume sugar from natural sources. |
| A．Sugar Is Everywhere. | B．Sugar Brings Happiness. |
| C．Why Does Sugar Taste So good? | D．Why Does Sugar Make Us Fat? |
【推荐2】After just a few days of training, dogs in Germany can be able to identify people who got COVID - 19, according to researchers. The dogs, part of a study by a university in Germany, were able to sniff (嗅出)out the virus exactly.
According to the study published in BMC Infectious Diseases, after receiving training for just five days, eight dogs from Germany's army could identify people with COVID - 19. They sniffed the saliva(唾液) of more than 1,000 people, both healthy and ill identifying the virus with a 94% success. "We think this works because people with the virus have completely changed their chemical smells, and we think that the dogs are able to sense the specific smell changes on those patients,“ Professor Dr. Maren Von said in a video on the study Thursday.
Dr. Holger Volk, another professor from the university, said that dogs have a sense of smell that is 1,000 times better than humans, so they have great potential(潜力) within the medical field. "We know for a very long time that dogs have been used in all walks of life, but for identifying patients, it's a new thing at present," Volk said. "People have not really realized the potential a dog could have to tell patients from healthy people.
1. What does the underlined word “this” in Paragraph 2 refer to?| A．The training of dogs in the army. |
| B．The patients' recovery from diseases. |
| C．The research into dogs by the Scientists. |
| D．The use of dogs in identifying the virus. |
| A．They are good at telling different smells. |
| B．They are familiar with the humans' saliva. |
| C．They have been serving in the army for a long time. |
| D．They have been trained to do the same work before. |
| A．Dogs' sense of smell is much better than humans'. |
| B．Dogs have been successfully used in other fields. |
| C．Dogs will play a role in the medical field. |
| D．Humans can't beat diseases without dogs. |
【推荐3】In general, just about every mammal (哺乳动物) relies on a community of gut bacteria (肠道细菌) for health and survival. Many animals have even developed to the point that closely related host species typically share more similar gut bacteria. But a new study has identified a converse phenomenon on one group of mammals — bats. The gut bacteria of closely related bats can be totally distinct from each other.
To learn about the relationships between bats and their gut bacteria, post-doctoral researcher Holly Lutz and her co-workers took samples of bacteria from the skin, tongues, and guts of 497 bats from 31 different species in Kenya and Uganda. They discovered bats have fewer bacterial species living in their guts than in their mouths and on their skin. What’s more, gut bacteria living in different bats are individually distinctive, following no apparent pattern. This struck the scientists as strange, since for most other mammals that have been studied, closely related hosts share more similar gut bacteria.
“There’s essentially no relationship between bats’ gut bacteria and their evolutionary (进化的) history,” says Lutz. While host identity is still an important factor in predicting the species of gut bacteria, this may simply be tied to where those bats live and what they eat. The fact that bats’ gut bacteria are more closely tied to where bats live than where those bats fall on the bat family tree indicates that developing a special relationship with just-right gut bacteria may not have been as important for bats as it has been for other mammals.
Lutz suspects that bats’ unique relationships with gut bacteria are related to the feature that sets them apart from other mammals: their ability to fly. “Bats have extremely shortened guts,” she explains. “Food takes just fifteen to thirty minutes to pass through a bat’s digestive system, a third as long as it would take for a similarly sized animal. That’s likely because a long, winding digestive canal would weigh the bats down.”
1. Which is closest in meaning to the underlined word “converse” in paragraph 1?| A．Typical. | B．Potential. | C．Inspiring. | D．Opposite. |
| A．Gut bacteria vary with related bats. | B．Mammals share similar gut bacteria. |
| C．There are 497 varieties of bats in Kenya. | D．Bats have the most bacteria in their mouths. |
| A．To quicken their food digestion. | B．To make them lighter for flight. |
| C．To help improve their ability to fly. | D．To fit in with their digestive system. |
| A．Bats contain a diverse range of bacteria. |
| B．Bats don’t seem to need gut bacteria to evolve. |
| C．Bacteria play a big role in bats’ health and survival. |
| D．Bats don’t rely on gut bacteria the way other mammals do. |
