Scientists are trying to make the deserts into good land again. They want to bring water into the deserts, so people can live and grow food. They are learning a lot about the deserts. But more and more of the earth is becoming desert all the time. Scientists may not be able to change the desert in time. Why is more and more land becoming desert? Scientists think that people make deserts. People are doing bad things to the earth. Some places on the earth don't get much rain. But they still don't become deserts. This is because some plants are growing there. Small green plants and grass are very important to dry places. Plants don't let the hot sun make the earth even drier. Plants don't let the wind blow the dirt away. When a little bit of rain falls, the plants hold the water. Without plants, the land can become a desert much more easily.

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    Could smells affect your lifespan? Female fruit flies (果蝇) without the ability to smell food live longer than other fruit flies．The sense of smell may be connected to the cellular ageing (细胞老化) process in many other living things  even people．Such connection has recently been found in both worms and flies．For example, scientists found that removing fruit flies' ability to smell made them live nearly 20 percent longer than flies with a sense of smell．

    They confirmed that food smells were the ones most likely to affect ageing, as nutrition (营养) and lifespan are known to be connected in many living things．To test the idea that food smells affect lifespan, they removed flies' ability to smell carbon dioxide, which is produced by some fly foods．They left the rest of the smelling system．

    This action had no effect on male flies, but the females lived 30 percent longer than normal．Removing the ability to smell CO₂ may stop flies getting information about food availability．This could mean that food is not enough, causing processes that encourage flies to survive．Scientists found that the female flies from stored extra fat and that both males and females immune (免疫) to CO₂ were stronger against the stress than normal flies．It is suggested that females may simply be easily influenced by the smells of CO₂ ．

    Scientists point out that people don't know whether ageing and smell are connected in animals and humans．But they clearly experience physical changes after smelling food．

    Man is a land animal, but he is also closely tied to the sea. Throughout history the sea has served the needs of man. The sea has provided man with food and a convenient way to travel to many parts of the world. Today, nearly two—thirds of the world's population live within 80 kilometers of the sea coast.

    In the modern technological world, the sea offers many resources to help mankind survive (=continue to live). Resources on land are beginning to be used up. The sea, however, still can be hoped to supply many of man's needs.

    The list of riches of the sea yet to be developed by man's technology is impressive. Oil and gas explorations have been carried out for nearly 30 years. Valuable amounts of minerals exist on the ocean floor ready to be mined (开采).

    Fish farming promises to be a good way to produce large quantities of food. The culture of fish and shellfish (贝类动物) is an ancient skill practised in the past mainly by Oriental people.

    Besides oil and gas, the sea may offer new sources of energy. Experts believe that the warm temperature of the ocean can be used in a way similar to the steam in a steamship. Ocean currents (水流) and waves offer possible use as a source of energy.

    Technology is enabling man to explor ever more deeply under the sea. The development of strong, new materials has made this possible.

    The technology to harvest the sea continues to improve. Experts believe that by the year 2000 the problems that prevent us from exploiting fully the food, minerals, and energy sources of the sea will be largely solved.

    Have you ever ridden a Ferris wheel lately? Can you imagine the flying feeling as you are pulled up to the top and then moved down to the bottom quickly again?

    Today a Ferris wheel is usually 40 to 60 feet tall. That seems very high when you are on the top looking down. But the first Ferris wheel was 264 feet high- taller than a twenty-story building! Can you imagine the view from the top of that?

    The first Ferris wheel was built for the 1893 World's Fair in Chicago. The people who planned the fair were looking for an attraction that would bring people to Chicago. George Ferris handed a drawing of a giant wheel that people could ride on. At first everyone laughed at his strange idea. But Mr Ferris did not give up, and finally the idea was accepted. The ride opened in June of 1893.

    Today's Ferris wheels have 12 to 16 seats, which each carry 2 or 3 people. But that first one had 36 enclosed cars, each holding 60 passengers. When filled, it carried 2,160 people. During that summer in Chicago, about 1.5 million people rode the Ferris wheel.

After the fair, the ride was moved to a nearby amusement park built especially to show off the wheel. In 1904, it was moved again一to St. Louis for the Louisiana Purchase Exposition. After the fair there, the wheel stood unused. In 1906, it was finally sold to a company for scrap metal(废金属).

    Luckily a Chicago bridge builder, W.E. Sullivan, figured out how to make a smaller Ferris wheel that could easily be taken apart and put together. In 1906, he started the company that still makes many of the Ferris wheels used today.

    But, whenever you ride one, remember that it all began with George Ferris's strange idea!

Hi, I'm a middle school student. I'm Judy. In my class there are thirty-eight students. How do they go to school every day? Seventeen of them take the bus because they live far from the school. Six students walk. They think walking is good exercise. Fifteen students ride their bikes to school because they like riding bikes very much and their homes are not far from the school. No one goes to school by car. How do you go to school? Haha, I'm one of the fifteen.

Hello, everyone! I'm Kevin. I'd like to tell you something about my dream home. My dream home is near the beautiful beach(沙滩). It is not big, but it is a nice and quiet place. 

My dream house has two floors. It is not high. But for our family, it is enough. At the back of our house, there is a garden. We can grow flowers that we like. On the first floor is the living room. We receive guests(客人) there. In my spar time, my young brother and I can play together there. Our bedrooms are on the second floor. One is for my parents and the other is for my brother and me. 

There is a bed in my bedroom. It's like a ship,and it's very soft. There is a desk with a computer on it. I can surf the Internet or play computer games. I can often do my homework on the desk. My favorite place is the balcony. I can walk out to look at the beach and look up at the sky. 

This is my dream home. What about yours?