Many people can use computers, but few of them know how to use them properly(合理地). Here are five suggestions for you when you use your computer.

1. Keep your computer in a cool, dry room. Computer work best at a temperature of 5ºC ~30ºC.

2. Do not smoke or let other people smoke cigarettes near your computer. Smoke of all kinds can cause many problems.

3. Do not eat or drink when you are near your computer. Pieces of food and some water in the keyboard can also cause many problems.

4. Make sure that keyboard and the screen(屏幕) are at the proper height for you. If not, you will get a backache.

5. Make sure the screen is at the suitable distance from your eyes. Keep your screen clean and do not have it too bright. A dirty screen can hurt your eyes. A very bright screen can also be bad for your eyes.

(     )46. What will happen to the computer when room temperature is below 0ºC?

A. It may become dirty.                B. It may break into pieces.

C. It may not work as well as usual.      D. It will be bad for your eyes.

(     ) 47. Your had better not eat or drink at the computer because _____________.

A. the food may cause problems         B. the food may taste bad

C. the screen will harm (伤害) you       D. the screen will be dark

(     ) 48. Which suggestion is about how to protect your eyes when you use a computer?

A. No.2.         B. No. 3             C. No.4         D. No.5 

(     ) 49. The title of this passage is most probably ______________.

A. How to use computers        B. How to cool computers

C. How to buy computers        D. How to clean computers

(     ) 50. The passage can most probably be found in a ____________book.

A. history     B. science     C. travel    D. math

                         

Fire can help people in many ways. But can also be very harmful. Fire can heat water warm your houses, give light, and cook food. But fire can burn things too. It can burn trees, houses, animals, or people. Sometimes big fires can burn forests.

Nobody knows for sure how people began to use fire. But there are many interesting, old stories about the first time a man or woman started a fire. One story from Australia tells about a man very, very long time ago. He went up to the sun by a rope and brought fire down.

Today people know how to make a fire with matches. Children sometimes like to play with them. But matches can be very dangerous. One match can burn a piece of paper, and then it might burn a house. A small fire can become a big fire very fast.

Fires kill many people every year. So you must be careful with matches. You should also learn to put out fires. Fires need oxygen. Without oxygen they die. There is oxygen in the air. Cover a fire with water, sand, or in an emergency, with your coat or something else. This keeps the air away from a fire and kills it.

Be careful with fire, and it will help you. Be careless with fire, and it will burn you.

51. Which is true?

A. We are not sure how people started to use fire.

B. It is an Australian who started a fire.

C. We know how people began to use fire.

D. Nobody knows how to make a fire.

52. Children mustn’t play with matches because ______.

A. matches burn paper

B. it is not interesting

C. matches can be dangerous

D. they don’t know how to make a fire with matches

53. If you are going to put out a fire, you ______.

A. must be careful with matches

B. ought to know it can be harmful

C. have to cover it with water only

D. should keep air away from it

54. We must be careful with fire, or it ______.

A. can be

B. warms our houses

C. might burn us

D. will help us

55. What is the main idea of the passage?

A. Fire can help people in many ways.

B. Fire can be both helpful and harmful.

C. Fire can burn things and people

D. We must be careful with matches.

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