Leaves are very important for trees—they give food to the whole tree (or plant)!
Do you know why leaves are green? That is because there is chlorophyll (叶绿素) inside leaves. It allows the leaves to conduct photosynthesis (光合作用). A plant makes its own food in its leaves. Water comes to the leaves through the roots. Air gets into the leaves through very small holes. It also needs sunshine because a plant can make food only when the sun is shining.
Leaves keep you cool on hot days by making shades. Leaves also help make trees good homes for animals, like birds, squirrels and bugs by providing them with shelter, a place to hide, and even food! They are not only helpful to animals but also humans.
As the weather gets cooler and the days get shorter in autumn, trees start to prepare for winter. Since leaves have water inside, they can’t stand low temperatures. Because the water would freeze and the leaves would die and fall. Another reason that trees lose their leaves is because bad weather (such as thunder-storms) hurts them during the spring and summer or they get ill.
Since they lose their leaves in autumn, they will be able to grow new ones in spring! When leaves fall to the ground, they finally break down and become nutrients for the soil, helping prepare for more plants to grow in spring and also create a layer that helps the ground take in water.
1. Why are leaves green?| A．Because air gets into the leaves. |
| B．Because there is chlorophyll inside them. |
| C．Because they can give food to the whole tree. |
| A．The plant | B．The water | C．The air |
| A．by listing numbers | B．by asking questions | C．by giving examples |
| A．2. | B．3. | C．4. |
相似题推荐
【推荐1】The ancient capital Xi’an in Northwest China’s Shaanxi Province has just held the National Games. As the capital of 13 dynasties throughout Chinese history, the ancient city has never been far from sports. Starting from the Western Zhou Dynasty (1046 BC—771 BC) to the Tang Dynasty (618 AD—907 AD), the city had held many sports events.
Cuju (蹴鞠) was an ancient Chinese competitive game involving (涉及) kicking a ball through an opening into a net. As the ancestor of soccer, it first appeared in the ancient Chinese historical work Zhan Guo Ce, which describes cuju as a form of entertainment(娱乐) among the common people.
Later, cuju was commonly played in the army for training, during the Han Dynasty (202 BC—220 AD). Emperor Hangaozu Liu Bang, the first emperor of the Western Han Dynasty, was a cuju fan. He not only liked watching cuju games, but always tried his footwork on the field. Liu Che, emperor Wu of the Han Dynasty, who was crazy about cuju, would build a cuju field wherever his army went. He used cuju as a way of training soldiers.
Up to the Tang Dynasty, women cuju players were very popular in the royal court (皇宫)，as emperors enjoyed watching cuju games. At that time, different kinds of skills were widely used in playing cuju, mainly serving as a form of entertainment.
As a way of national culture protection, cuju was listed into China’s intangible cultural heritages (非物质文化遗产) in 2006.
1. Which dynasty built its capital in Xi’an for the first time?| A．The Western Zhou Dynasty | B．The Tang Dynasty |
| C．The Han Dynasty | D．The Western Han Dynasty |
| A．Zhan Guo Ce shows that cuju was an ancient Chinese sport which was popular. |
| B．Most of the emperors of the Han Dynasty were crazy about cuju. |
| C．Women in the Tang Dynasty were trained to join in the army. |
| D．Cuju isn’t China’s intangible cultural heritage now. |
| A．In an art magazine. | B．In a sports magazine |
| C．In a music book. | D．In a guidebook. |
【推荐2】We have all been there. It’s 3 o’clock and you’ve been hard at work. As you sit at your desk, a strong desire for chocolate overcomes you. You try to busy yourself to make it go away. But it doesn’t. In fact, the more you try NOT to think about a square of deep, dark chocolate melting in your mouth, the more you want it. You can even smell it!
A food craving is a strong desire for a specific type of food. And they are normal. Most people have them even though what we crave might be different. One person might crave sweet chocolate, while another might crave salty potato chips.
Sometimes the foods we crave are not super healthy ones but rather fatty or sugary foods. Or sometimes we crave foods from our childhoods, like American meatloaf, Polish pirogues or Vietnamese pho. Other times the cravings may be for something healthy but very specific, such as Japanese sushi or Korean kimchi.
But where do food cravings come from? And how are they different from hunger?
Scientists at the website How Stuff Works compare hunger and cravings this way. Hunger is a fairly simply connection between the stomach and the brain. They even call it simply “stomach hunger.”
The website explains that when our stomachs burn up all of the food we have eaten, a hormone sends a message to one part of the brain, the hypothalamus, for more food. The hypothalamus (丘脑下部)regulates our most basic body functions such as thirst, hunger and sleep. The brain then releases a chemical to start the appetite. And you eat.
A craving is more complicated. It involves several areas of the brain. These areas make up the reward center of the brain. A craving can also be tied to our mental state and memory. So, some scientists call food cravings “mind hunger.”
In a 2007 study, researchers at Cambridge University found that “dieting or restricted eating generally increase the probability of food craving.” So, the more you deny yourself a food that you want, the more you may crave it. However, fasting is a bit different. They found that eating no food at all for a short period of time, lessened food cravings.
So, the next time you crave food from your childhood or have a strong desire for something very specific, know that your brain may be more to blame than your stomach.
1. How are cravings different from hunger?| A．Hunger is a fairly simply connection between the stomach and the brain. |
| B．A craving can also be tied to our mental state and memory. |
| C．The more you deny yourself a food that you want, the more you may crave it. |
| D．Scientists call hunger “stomach hunger” but cravings “mind hunger”. |
| A．Vietnamese pho | B．Korean kimchi | C．Swiss black chocolate | D．American meatloaf |
| A．eating no food for a period of time |
| B．happening, moving, or doing something at great speed |
| C．tightly and firmly |
| D．not changing your mind |
| A．If you go on a diet, it’s more likely for you to crave food. |
| B．When we crave food, it shows that we are hungry. |
| C．We eat when our brain releases a chemical to start the appetite. |
| D．The foods we crave are not super healthy ones but rather fatty or sugary foods. |
Migu Video is now showing the BBC documentary, One Cup, A Thousand Stories. It was filmed for three years in 13 countries across six continents(大洲),
The creators from Britain and China had first listed a lot of themes, such as traditional Chinese medicine, new technologies and so on,
“Tea is China’s great gift to human. We wanted to look at how tea
The documentary has already won praise from audiences in China. It will run on the BBC Earth channel for Asia during the 2022 Lunar New Year holiday, as a try to promote(推广) tea and its culture to overseas audiences.
| A．giving the audience(观众) a chance to examine tea’s influence |
| B．and its influence on people’s lives around the world |
| C．but tea was finally picked as the theme |
| D．and tea culture developed in China and spread across the world |
| E．so it is a good subject on which to work together |
【推荐1】Children under age 6 should try their best not to use cellphones or computers, the National Health Commission has said, in a bid to protect them from nearsightedness. The commission also advised against parents using electronics before their children. The advice came when the commission recently made public the results of a survey on nearsightedness among children and youths.
The survey found that 53. 6% of Chinese children and teenagers had suffered from nearsightedness in 2018. The nearsightedness rate was 14. 5% for 6-year-olds in kindergarten, 36% for primary school students, 71. 6% for junior middle school students, and 81% for senior high school students.
The commission said age 0-6 is a serious time to develop the ability of seeing, and special importance should be put on the protection and health of eyesight at an early stage. It added that the most important cause of nearsightedness is that children spend too much time watching cellphones, computers and televisions.
At primary and middle schools, teaching with electronics should be controlled to no more than 30% of overall teaching time. After classes, students should take a rest of 10 minutes after using electronic products for learning for 30-40 minutes. Children shouldn't spend more than one hour a day using electronic products for fun.
In addition, the commission made suggestions on outdoor exercise. It said children and teenagers should control the continuous use of eyes in reading and writing to no more than 40 minutes and leave enough time for outdoor activities in the daytime. Teachers and parents should guide children to actively take part in exercise, with around two hours of outdoor activities in the daytime.
China made a plan last year to stop the rise in nearsightedness among children and teenagers. It wants to keep the nearsightedness rate among 6-year-olds at around 3% by 2030, and the rate among junior and senior high school students below 60% and 70%.
1. What does the underlined word "electronics" refer to?| A．Cellphones and computers. | B．Letters and cellphones |
| C．Computers and magazines. | D．newspapers and computers |
| A．kindergarten | B．primary school | C．junior high school | D．senior high school |
| A．Kids spend too much time on their homework. | B．Kids spend too little time doing eye exercises |
| C．Kids spend much time on electronic products | D．Kids spend too little time doing outdoor exercise |
| A．it's very bad for kids to use electronic products | B．children should use electronic products properly |
| C．children should use electronic products in class | D．it's difficult for kids to use electronic products |
【推荐2】We often go to the library to read books. But it is different in Afghanistan, Children there can not often read books in the library.
Look! Here comes a big bus! Are the students taking the bus to school? No. They’re going to read books on the bus. The bus is a mobile library. The kind girl Freshta Karim wants to help the kids in Afghanistan. She changes a bus into a library. There are a lot of books on it.
The driver drives the bus around Kabul everyday. He usually parks the bus by the roadside, Kids can visit it after school. They can read for 2 hours on the bus every time. Like other libraries, they can’t talk on the bus.
1. What do students take the bus to do?
| A．To visit their new schools. | B．To go for a picnic. |
| C．To read books. | D．To celebrate a festival. |
| A．移动的 | B．废弃的 | C．崭新的 | D．私家的 |
| A．She buys a bus for them. |
| B．She gives them a place to read books. |
| C．She teaches them to write. |
| D．She gives them food. |
| A．stand up | B．take food | C．keep quiet | D．listen to music |
| A．Busy. | B．Kind. | C．Cool. | D．Lazy. |
【推荐3】Frogs produce a lot of eggs up to 4, 000 eggs! However, there are a lot of things happening to tiny little frog eggs. Eggs can be eaten, broken, or washed away. Only about half of the eggs can come out. Sometimes, the mother may stay with the eggs to take care of them. Sometimes, the mother may leave and not come back to the eggs. A baby frog stays in the egg for 6 to 21 days before it comes out.
When the baby frogs leave their eggs, they are called tadpoles (蝌蚪). The tadpoles are green or brown. This helps them hide in the algae (水藻). Many fish will eat the tadpoles. They will start swimming around more and eating the algae after about a week. The tadpoles will stay together and swim.
After the baby frog has been a tadpole for about a month, it starts to change again. The tadpole starts growing the lung (肺). The little tadpole also starts to grow back legs. As it grows more, the tadpole can eat bugs and some plants. The tadpole is stronger, and doesn’t hide as much.
When it is six to nine weeks old, the little tadpole grows front legs. Its lung begins working. The tadpole’s mouth gets bigger and it looks more like a frog. By the time it is twelve weeks old, the little frog will just have a tiny tail and will begin living on land.
1. How many days may a baby frog stay in the egg?| A．For 11 days. | B．For 5 days. | C．For 25 days. | D．For a month. |
| A．They swim together. |
| B．They hide in the algae. |
| C．They change colors. |
| D．They stay with their mothers. |
①Baby frogs start eating the algae ② Baby frogs eat some plants.
③Baby frogs grow front legs. ④Baby frogs leave their eggs.
⑤Baby frogs start living on land. ⑥Baby frogs start growing lungs.
| A．④①⑥②③⑤ | B．④①⑤②③⑥ | C．④①②③⑥⑤ | D．③⑥①⑤②④ |
| A．Both tell how tadpoles are able to live on land. |
| B．Both tell how tadpoles live by hiding. |
| C．Both tell how frogs change during their life. |
| D．Both tell how frogs are able to live in the water. |
【推荐1】It is quite normal for us to poop（拉粑粑）. But do plants poop? They do, in fact. But plants poop differently from us. They poop to get rid of（除掉）things they can’t use or that might hurt them.
The Venus flytrap（捕蝇草）is one example. This plant eats insects with its “mouth” —two big leaves. It can eat the soft parts of insects, but can’t eat the insects’ harder parts. So the flytrap opens its “mouth” to get rid of the hard parts. You can think of this as the plant pooping.
But actually, the way that plants get rid of salt or other things is more poop-like. They get rid of them through their leaves, bark and roots. For example, mangrove（红树林）trees often grow in salty water. They take in a lot of salt from the water. They will move most of the salt to their leaves. As time goes by, the leaves take in a lot of salt. Finally, the leaves fall off the trees, taking the salt with them.
1. What does the Venus flytrap use to eat insects?
| A．Its flowers. | B．Two big leaves. | C．Its bark. | D．Its roots. |
| A．The soft parts of insects. | B．The harder parts of insects. |
| C．The salt in insects’ bodies. | D．The insects’ poop. |
| A．By moving it to its leaves and letting them fall off. |
| B．By taking in more salt through its roots. |
| C．By washing its leaves in water. |
| D．By losing its bark. |
| A．Why we need to poop. | B．Why insects are important. |
| C．How some plants poop. | D．How to keep plants healthy. |
| A．National Geographic. | B．Science World. | C．News Week. | D．Photography. |
【推荐2】Every living thing needs to reproduce. Reproducing means creating more members of your group. In order for plants to reproduce, they have to spread their seeds (种子) to other areas. Plants have developed all kinds of ways to do this.
The simplest way is gravity. Many seeds are inside of fruit. When a piece of fruit gets too heavy, it falls from a tree to the ground. Sometimes animals will pick up the fruit and drop it in another area. That helps move the seed even farther away. Apples spread this way.
Other plants use wind to spread their seeds. Dandelions are a good example of this. Dandelion seeds are so light that when wind blows, it carries dandelion seeds to new places. Maple (枫树) seeds also use wind. Their seeds are connected with long, thin leaves that look like wings. When the seed falls from the tree, its “wings” help it fly farther from the tree.
Some animals help plants spread their seeds. The animals eat the seeds. While the seed is in the animal’s body, it stays whole. When the seed leaves the animal, it’s in a new place.
Ants also help spread seeds. Some seeds have a special smell that attracts ants. The ants bring the seeds back to their home, which of course is underground. They only eat part of the seed. They leave the rest of the seed underground. After that, the seed can start growing.
1. What does the word “gravity” mean in the second paragraph?| A．The action that makes animals drop seeds. | B．The help that moves seeds even farther away. |
| C．The need that comes from animals and plants. | D．The force that causes fruit to fall to the ground. |
a.They only eat part of the seed.
b.They help seeds fall from the tree.
c.They carry seeds to the underground home.
d.They pick up the fruit and move it far away.
e.They leave the rest of the seed underground.
| A．b, d, e | B．a, b, d | C．a, c, e | D．b, c, d |
| A．Nature. | B．Culture. | C．Education. | D．Technology. |
| A．How Plants Spread Seeds? | B．Why Animals Pick Up Seeds? |
| C．How Wind Helps Seeds Spread? | D．Why Seeds Have a Special Trip? |
【推荐3】In the first quarter of this year, sales of vegetable seeds (种子) on Tmall doubled compared to last year, according to a report on balcony (阳台) gardening.
The report shows Shanghai, Dongguan, and Beijing are the top three cities for urban vegetable growers, who are mainly in their 20s and 30s. And right now, these farmers in the city are probably enjoying the fruit of their hard work.
Han Yijun, director of the National Agriculture Research Center at the China Agricultural University, says that growing vegetables in balcony gardens is more than just a skill. It is becoming a popular lifestyle.
Having fun and seeing the results are both important for the urban farmers. As living standards improve, they have changed their taste in vegetable varieties (品种). They prefer to grow vegetables that are fresh-looking and also make their balconies colorful. Compared with vegetables grown in fields, those grown in balcony gardens are greater in variety, easier to plant, and better for the environment.
The growers also enjoy posting photos of their colorful tomatoes on social media or exchanging tips on growing in group chats. Such actions create great social value.
For children, balcony gardening is a great way to stay away from screens and enjoy nature. It also helps them know about farm work and develop a sense of responsibility (责任感).
1. What does the underlined word “urban” probably mean?| A．熟练的 | B．富裕的 | C．疲惫的 | D．城市的 |
| A．Easier to plant. | B．Better for the environment. |
| C．Healthier to eat. | D．Greater in variety. |
| A．How to enjoy nature without going out. |
| B．How to grow vegetables in balcony gardens. |
| C．Why balcony gardening is good for children. |
| D．Why children should stay away from screens. |
| A．Health. | B．Life. | C．Family. | D．Food. |
