perfect storm.

28. What do we know about tornadoes?

A. They can be predicted by satellites. B.They usually come down in winter

C. The warning time for them is very short . D. They often develop into storms.

29. A turtle probe is used to .

A. predict tornadoes B. collect information about tornadoes

C. chase tornadoes D. decrease the power of tornadoes

30. The third paragraph is mainly about .

A. how tornadoes develop B. how the turtle probe works

C. how powerful Tornado Alley is D. how Samaras chases a tornado

31. According to the text ,the job of a tornado chaser is .

A. difficult and dangerous B. stressful and troublesome

C. mysterious and interesting D. exciting and popular

　　　　　　　　　　　　　　　　　　D

　　"I will think of it "It is easy to say this ; but do you know what great things have come from thinking? We can not see our thoughts, or hear, or taste , or feel them; and yet what strong power they have！

　　Sir Isaac Newton was seated in his garden on a summer evening, when he saw an apple fall from a tree. He began to think, and, in trying to find out why the apple fell, discovered how the earth, sun, moon, and stars are kept in their places.

　　A boy named James Watt quietly by the fireside, watching the lid(盖子) of the tea kettle as it moved up and down. He began to think; he wanted to find out why the steam in the kettle moved the heavy lid. From that time he went on thinking and thinking; and when he became a man, he improved the steam engine so much that it could, with the greatest ease , do the work of many horses.

　　James Ferguson was a poor Scotch shepherd(羊倌) boy. Once, seeing the inside of a watch, he was filled with wonder ."Why should I not make a watch?" he thought. But how was he to get the materials out of which to make the wheels and the mainspring(钟表等的主发条)? He soon found how to get them: he made the mainspring out of a piece of whalebone. He then made a wooden clock which kept good time. He began, also, to copy pictures with a pen, and portraits(肖像) with oil colors. In a few yeas, while still a small boy, he earned money enough to support his father. When he became a man, he went to London to live. Some of the wisest men in England, and the king himself, used to attend his lectures. His motto was, "I will think of it ,"and he made his thoughts useful to himself and the world.

　　When you have a difficult lesson to learn, don't feel discouraged or ask someone to help you before helping yourselves. Think, and by thinking you will learn how to think to some purpose.

32. What can we learn about James Ferguson?

　　　A. He was born in a rich family B. His wooden clock seldom worked well

　　　C. He was a painter from England D. His mind greatly influenced the world

33. Which word can best describe the three scientists mentioned in this text?