We all enjoy the colors of autumn leaves. 【小题1】 To answer this question, we first have to understand what leaves are and what they do.

Leaves are nature’s food factories. Plants take water from the earth through their roots and take carbon dioxide from the air. 【小题2】 Plants use the sugar as food for energy. The way plants turn water and carbon dioxide into sugar is called photosynthesis(光合作用). Chlorophyll(叶绿素) helps make photosynthesis happen. Chlorophyll gives plants their green color.

As summer ends and autumn comes, the days get shorter and shorter. 【小题3】.

During winter, there is not enough light or water for photosynthesis. Trees will rest and shut down their food-making factories. There is no chlorophyll in the leaves. As the bright green fades away, we begin to see yellow and orange colors. 【小题4】 We just can’t see them in summer because they are covered by the green chlorophyll.

The bright reds we see in leaves are made mostly in autumn. In some trees, like maples(枫叶), sugar is kept in the leaves after photosynthesis stops. 【小题5】 The brown color of trees like oaks is made from the wastes which are left in the leaves.

All these things make the beautiful colors we enjoy in autumn.

We all know that eating junk food can make us fat. However, a new study suggests that it can do more than that – it can also make us lazy, reported CBS News.

In the study, researchers at the University of California, Los Angeles, US divided 32 female rats into two groups. The first group was fed a diet of healthy food such as corn and fish, while the second was given a diet of highly processed (加工的) food rich in sugar, namely “junk food”.

Within three months, the rats in the second group were already much fatter than those on the healthy diet. And when researchers trained the rats to do simple tasks, they found even more differences between the two groups rather than weight.

During the task – pushing a lever (杠杆) to receive a reward of sugar water – the rats on the junk food diet were found to be less willing to move, and they took longer breaks between each push than the lean rats did.

“It is as if the rat is thinking ‘This is too much work’,” Aaron Blaisdell, leader of the study, told the Los Angeles Times.

But what about the possibility that the fat rats were less passionate about getting sugar water because they were already eating lots of sugar in their daily diet? That’s why researchers repeated the tests by rewarding fat rats with plain water when they were extremely thirsty. However, the results came out just the same.

According to researchers, these differences suggest that junk food changed the chemistry in the rats’ brains.

The experiment didn’t end there. After six months, the rats’ diets were switched, and the overweight rats were given a healthy diet for nine days. However, this change didn’t help reduce their weight or improve their ability to perform tasks, which means the effects of their junk food diet persisted (持续存在). “There’s no quick fix,” said Blaisdell.

For a long time, we’ve believed that people become fat because they are lazy. But this study has proven the opposite to be true as well, which indicates that laziness and obesity are a “vicious cycle (恶性循环)”.

So, if you constantly feel tired, lacking any urge to get up from your chair, it could be that you’ve been studying too hard. But you should also pay attention to your diet.

Shrinking Storm on Jupiter （木星)

It’s snowing, but the clouds are red. The wind howls at 400 miles an hour, faster than a hurricane. And it’s colder than the North Pole. Named the Great Red Spot, this storm is on Jupiter, the largest planet that goes around the Sun. The storm is shrinking. No one knows why — or what it will do next.

Astronomers discovered the Great Red Spot by looking at Jupiter through telescopes. The spot, once estimated to be 25,500 miles across, was just 10,250 miles wide when the Hubble Space Telescope last observed it. “It’s at the smallest size that we’ve ever seen. ” says Dr. Amy Simon, an astronomer who studies the storm. It’s also changing shape, looking more like a circle than its usual oval.

Jupiter differs greatly from Earth. It’s made mostly of hydrogen and helium（氦). But most of the hydrogen and helium on Jupiter is not in the form of gas. Instead, Jupiter’s great gravity squeezes the hydrogen and helium, turning most of these elements into a liquid. Only the outer part of Jupiter is gas. And that’s where the Great Red Spot is. No one knows why the Great Red Spot is red. Like Jupiter’s air, the spot is made mostly of hydrogen and helium gases. But they have no color. So something else must color the spot red.

Mysteries abound about the spot, such as what powers it and why it is so red. Now another one arises. The Great Red Spot has lasted longer than any storm on Earth. On Earth, hurricanes weaken when they move from sea to land, and when they move north or south. Neither of these things happens on Jupiter. Yet the storm is shrinking. “Could it disappear? ” asks Dr. Simon. “Would I bet money on it one way or the other? Probably not. ”