阅读理解

When settlers (移民）came to America during the 1600s, they were surprised to find so many trees. Some trees were so huge that a large man could not put his arms around them. Those trees helped the settlers a lot. They were glad and thankful to have these trees. They used them to build houses and make fire. From the wood of the trees, they made furniture, tools and so on.

Most people thought the forests would last forever. However, by 1800, America had its first wood shortage (短缺). How did it happen? People had not known that trees were being cut down faster than new ones could grow.

Some American people made trips to foreign countries. There they saw destroyed forests and learnt the importance of protecting forests. They came back to the United States and warned that if Americans didn't use trees more carefully and wisely, someday the forests would all be gone. However, people were not ready to listen. Years went by, and America's forests kept disappearing. It made some people really worried. But they did nothing.

Finally, J. Sterling Morton, the man who is remembered as the father of Arbor Day (过节), got people to listen. He named a Tree-Planting Day, or Arbor Day. He worked hard to make Arbor Day a national holiday. On that day, people usually plant a lot of trees.

Today, millions of trees have been planted in the United States because of Arbor Day. Arbor Day is such a good idea that many other countries now also have Arbor Day. Many, many trees are being planted all over the world because of J. Sterling Morton's work.

    Like most people, your intelligence（智力）changes from season to season. You are probably a lot sharper in spring than you are at any time of the year. A well known scientist, Ellsworth Huntington concluded（得出结论）from other men's work and his own that climate and temperature have a clear effect on people's intelligence.

    He found that cool weather is much better for creative thinking than warm weather, but this doesn't mean that all people are not so quick at learning in summer as they are during the rest of the year. It doesn't mean, however, that the intelligence of a large number of people seems to the lowest in summer.

    Spring season appears to be the best period of the year for thinking. One reason may be that in spring man's intelligence is affected（影响）by the same factors（因素）that bring about great changes in all nature.

    Autumn is the next-best season, then follows winter. As for summer, it seems to be a good time to take long holidays from thinking.

    When you are waiting for a bus at a station, a 31-metre-long bus is coming to you. You must be surprised. In fact, the 31-metre-long bus is the longest bus in the world. And the bus comes from Germany. An ordinary bus is only about 10 metres long and it can carry only 80 people once. But the longest bus can carry 256 people. So we will need fewer buses in the future. The longest bus can save energy, too. That's to say, it will take less energy than an ordinary bus. Moreover, the driver can drive the longest bus as easily as an ordinary one.

    However, firstly, it has to spend $ 10, 000, 000 buying the longest bus. Someone jokes that we can buy a lot of ordinary buses with that money. Secondly, people think that it is hard for the longest bus to travel on the bustling streets. It may cause new traffic problems. Thirdly, it is easy for someone to get onto the bus without buying a ticket.

    Everybody hates rats. But rats may soon be man's new good friends. What happens after an earthquake? We send in rescue dogs. Why? Because they can smell people. Dogs save lives. They help rescuers to find living people. But dogs are big and they can't get into small spaces. So now a new research project is using a smaller animal to save lives: the rat.

    How does it work? First, the rat is trained to smell people. When this happens, the rat's brain gives a signal. This is sent to a small radio on its back, and then the rescuers follow the radio signals. When the rat's brain activity jumps, the rescuers know that someone is alive. The rat has smelled that person.

    Although there are already robots which can do this job, rats are better. Robots' noses don't work well when there are other smells around. Rats are good at that. Rats can also see in the dark, they are cheaper and quicker to train than dogs, and unlike robots, they don't need electricity!

    The "rat project" is not finished. But a scientist says, "It would be great. A rat could get into any place we couldn't get to, and a rat would get out if it wasn't safe." Perhaps for the first time in history, people will be happy to see a rat in a building (but only after an earthquake, of course).

    There are many animals in danger, such as pandas, elephants, and South China tigers.

    The South China tiger is the smallest tiger in Asia. It is also one of the rarest tigers in the world. Scientists think that there might be a few South China tigers living in the wild, but they are still not sure about it.

    The South China tiger is special in its face, but it shares the height with the common tigers. In the past, the South China tigers lived in the forests. But today more than half of them are living in zoos. If there are not safe places for them, they will die out soon. Baby South China tigers need their mothers' milk in the first two months. The mother teaches her babies how to hunt.

    Scientists think that people should do something to protect the rare animals. If people take action together, these animals will have a better place to live in. We'll also live in a better world.