The world is not hungry, but it is thirsty. It seems strange that nearly 3/4 of the earth is covered with water while we say we are short of water. Why? Because about 97% of water on the earth is sea water which we can't drink or use for watering plants directly. Man can only drink and use the 3%--- the water that comes from rivers and lakes. And we can't even use all of that, because some of it has been polluted. Now more water is needed. The problem is: Can we avoid a serious water shortage later on? First we should all learn how to save water. Secondly, we should find out the ways to _ it. Scientists have always been making studies in the field. Today, in most large cities water is used only once and then runs to the sea or rivers. But it can be used again. Even if every large city reused its water, still there would not be enough. What could people turn to next? The sea seems to have the best answer. There is a lot of water in the sea. All that needs to be done is to get the salt out of the sea water. This is expensive, but it's already used in many parts of the world. Scientists are trying to find a cheaper way of doing it. So you see, if we can find a way out, we'll be in no danger of drying up. ,,. From the passage we learn _ . A) if every city reused its water, we'll be in no danger of drying up B) man can only drink and use about 25% of water on the earth C) today in most large cities water is used only once D) water can be used only once
C

Computers are useful machines. They can help people a lot in their daily life. For example, they can help people to save much time to do more work, and they can help people to work out many problems they can't do easily. Our country asks everyone to learn to use computers before the twenty-first century, except the old people. Today more and more families own computers. Parents buy computers for their children. They hope computers can help them improve their studies in school. However, many of their children use computers to play games, to watch videos or to sing. The teachers and parents complain that computers can not help children to study but make them fall behind. So computers are locked in boxes by parents. In some other countries, even some scientists also hate computers. They say computers let millions of people lose their jobs or bring them a lot of trouble. Will computers really bring trouble to people or can they bring people happiness? It will be decided by today's students themselves! Why do we say the computer is a useful machine? Because _ . A) our country asks us to learn it B) it can help us a lot C) we can use it to play games D) it can help us to find jobs
B

Once there were two crows whose opinions were always opposite. One day, one of the crows said to the other, " You should realize, of course, that I can fly much higher than you." " Don't be ridiculous ." the other crow said. " Everyone knows that I can fly much higher than you." "No, you can't" the first crow said. "Yes, I can" the second crow replied, and the argument went on and on. At last they decided to have a contest to solve the argument. " We will compete to find out who can fly higher while carrying a bag" the first crow said. They argued for some time because of the size of the bag, but at last _ . Then there was a further argument about what each bag would be filled with. Finally, they agreed that the first crow would fill his bag with cotton and the second crow would fill his with salt. The first crow thought he was clever to agree to this, because salt is much heavier than cotton. At last they were ready for the contest. Holding their bag in their mouths, they flew into the sky. They had not been flying for long. However, when it began to rain- as the second crow had expected it would. Can you guess who could fly higher? The second crow filled his bag with salt because he thought _ A) salt was lighter B) cotton was heavier C) it would rain D) he would need some salt
C