There is little rain in desert. Because deserts are so dry, they have no "quilt" to help stop the soil from going away. As a result, they may get very hot during the day with the sun shining, but don't hold the heat overnight. Many deserts can quickly get cold once the sun goes down. Some deserts can reach temperatures of over 100 degrees F during the day and then drop below freezing (32 degrees F) during the night.

The largest hot and dry desert in the world is the Sahara Desert in Northern Africa. The Sahara is a sandy desert with great sand hills. It covers over 3 million square miles of Africa. Other large deserts include the Arabian Desert in the Middle East, the Gobi Desert in Northern China and Mongolia, and Kalahari Desert in Africa.

Animals that live in the desert are also used to needing little water. Many get all the water they need from the food they eat. Other animals keep water that they can use later. The camel stores up fat in its hump while other animals keep something they need in their tails.

Only certain types of plants can live in the terrible environment of the desert. You won't see a lot of tall trees in the desert. Most plants have a way to keep water in their leaves, or trunks so they can live a long time without water.

Now deserts cover around 20% of the world's land, but they are growing. This is called desertification and is caused by different reasons including human activities. The Sahara Desert is growing larger and larger each year. What should we do with it ?

    The world itself is becoming much smaller by using modern traffic and modern communication. Life today is much easier than it was hundreds of years ago, but it has brought new problems. One of the biggest problems is pollution.
    To pollute means to make things unfit or unclean to use. Pollution comes in many ways. We see it, smell it, drink it and even eat it. Pollution is beginning to threaten (威胁) our health, our happiness and our life.
    Man has been polluting the earth from the time he first made fire, washed his clothes in the river and threw his waste on the ground. When land was used up or water became dirty, men moved on to another place. At first, the problem was not so serious because there was plenty of clean air, land and water. There weren't so many people then and their wants fewer. All the dirty things could be absorbed(吸收) by nature and soon covered over. But this is no longer true. The increase of pollution and the development of industry(工业) have changed that. Man is slowly poisoning(毒害)not only his environment but also himself.
    Through the use of poison, man has polluted the land, killing the animals. By putting dirty water and chemicals into rivers and lakes we have polluted our drinking water, killing the fish.
Our increasing population is part of the problem. More people, more waste.
     Where is this all to end? Are we turning the world into a big rubbish dump(堆存处)，or is there any hope that we can get rid of (摆脱，除去) the pollution? Luckily, millions of people have been warned of the danger of pollution. Large numbers of people are now working hard to bring pollution under control.
    The earth is our home. We must take care of it. This means keeping the land, air and water clean. And we must take care of the rise in pollution at the same time.

阅读下面短文, 根据短文内容, 从短文后各题所给的A、B、C、D四个选项中, 选择最佳选项。

C

    A desert is a difficult place for animals to live, and some have unusual ways of making a living. The Texas lizard has a strange way to keep itself safe. When a predator(掠食动物) gets too close, blood goes out from the lizard's eyes. Then it breathes in much air to make its body look bigger. Another interesting desert animal is the javelina. To make a predator afraid and run away, the javelina bravely faces the animal. It makes a big noise with its teeth. It raises the hard hairs on its back to make itself look bigger. The javelina also gives off a strong smell as a warning when it is afraid. This smell is so strong that javelinas are also called "smelly pigs". Javelinas keep safe by staying close to their family, so there's a good chance they can make a predator change its mind!

    You might think a rain forest would be easier to live in than a desert. After all, there's plenty of food and water in a rain forest. But that also means a lot of animals live there. Being able to climb trees is a useful skill in the rain forest. It allows an animal to keep away from predators. The sloth spends most of its life in the treetops. Its strong, curved claws(爪子) help it climb and hang upside down from branches. The sloth also moves very slowly. It does this so it's not noticed. The aye-aye lives only in the rain forest of Madagascar, near Africa. The aye-aye is a night animal. This helps it to stay safe from daytime predators. However, the number of the aye-aye keeps going down and they may die out. People have hunted it because they think it brings bad luck. Also, much of the rain forest in Madagascar has been cut down, which has destroyed the aye-aye's home. Today there are laws(法律) to keep people from killing it.

    If you go shopping in any toy store, you can see clearly the differentgames and toys for boys and girls: there are a lot of pink toys on one side ofthe store for girls; and dark colored cars, guns, and soldiers for boys. Somebig stores with toys may even have a pink floor for girls and a blue floor forboys. In fact, it is difficult to buy a toy for a girl that is not pink.

    Somepeople think that too much pink is bad for girls. Sue Palmer, writer of ToxicChildhood, is very worried that most girls over the age of three are crazyabout the color. According to some scientists, this happens for two reasons. Firstly,most companies offer too many products in pink. Also, many parents think theirlittle daughter looks cute in pink. Sue Palmer says that girls at this agecannot make proper decisions by themselves, but the pink can affect (影响) the choices and thedecisions they will make in the future.

    Someparents are worried too-for example, Vanessa Holburn, thirty-two, who has twogirls under the age of four. Their bedrooms are a sea of pink and Vanessa isnot happy. "Pink says that you are soft and gentle. Blue says that you arestrong and powerful. I want my daughters to be strong and powerful. I'm worriedthat pink will not help them with that,"she says.

    Butnot everyone thinks there's something wrong with pink. Grayson Turner is afather of three girls and he isn't worried at all. "People forget thatthings change all the time," he says. "My girls used to love pink whenthey were little, but as they get older, they change." Turner explainsthat his twelve-year-old daughter never wears pink clothes anymore. "Thislove of pink is just a fashion and all fashions change," he adds. "It'sonly since the 1940s that people have started dressing girls in pink-beforethat it was a color for boys."

    This is a street crossing. There are red and green lights at each corner. Drivers must watch the lights carefully.

    When there is a green light, the cars may go on. When there is a red light, the cars must stop.

    They must wait until the red light changes (变成)to green. Then they can go on. Sometimes the cars want to make a right turn or a left turn. They can make a right turn when the light is green or red. But they must wait until the green light is shining (闪亮) if they want to turn left. Some people are color-blind (色盲的). They can't see the difference (不同点) between red and green. These people mustn't drive, or there may be an accident (事故) .We must keep our street safe (安全的).

The weather is getting hotter and hotter. You are thirsty playing basketball or riding home from school. A cold drink may be just the thing. But be careful what you are drinking. Something that looks cool may not be good for your health.

There are plenty of "energy drinks" advertisement on TV. Most of them have beautiful colors and cool names. They tell you they are helpful to your health. Sounds great and lots of people believe them!

But after a careful check you may find that most energy drinks have lots of caffeine (咖啡因) in them. These drinks are especially aimed at young people, students, busy people and sports players. Makers sometimes say their drinks make you better at sports and can keep you awake. But he careful not to drink too much.

Caffeine makes your heart beat fast. Because of this, the International Olympic Committee has limited (限制) its use. Caffeine in most energy drinks is as strong as that in a cup of coffee or tea. Possible health dangers have something to do with energy drinks. Just one box of energy drink can make you nervous, have difficulty sleeping and can even cause heart problems. Scientists say that teenagers should be discouraged from taking drinks with a lot of caffeine in them.