What _____ to Joan last night? What did she cry for?

　 A. was happened 　 B. happened

　 C. was happening 　 D. had happened

Force other than damaging winds are also at work inside tornadoes. Sometimes, as the turning, jumping funnel(漏斗) passes over a house, the walls and ceiling burst apart as if a bomb had gone off inside. This explosion(爆炸) is caused by the low air pressure at the center of a tornado.

The pressure at the center of a tornado is usually 13 pounds per square inch. However, inside the house the air pressure is normal, about 15 pounds per square inch. The difference of 2 pounds per square inch between the inside and outside pressure may not seem like much. But suppose a tornado funnel passes over a small building that measures 20 by 10 by 10 feet. On each square inch of the building, there is 2 pounds of pressure from the inside that is not balanced by air pressure outside the building. On the ceiling, that adds up to an unbalanced pressure of 57,600 pounds. The pressure on the four walls adds up to 172,800 pounds.

If windows are open in the building, some of the inside air will rush out through them. This will balance the pressure inside and outside the building. But if the windows are shut tightly, the great inside pressure may cause the building to burst.

　　Unfortunately, heavy rain happens in thunderstorms that later produce tornadoes. So, people often shut all windows to protect their property. This may cause far worse damage later.

1. Which of the following is the main topic of the passage?

A. Where tornadoes are formed. 　　　　 B. When tornadoes usually occur.

C. How tornadoes can be prevented.　　　　 D. Why tornadoes cause so much damage.

2. According to the passage, tornadoes can destroy building because the _____.

A. force of a tornado increases the air pressure in a building

B. air pressure at the center of a tornado is over 172,000 pounds

C. weight of a tornado can crush a building’s roof when it passes overhead

D. air pressure inside a tornado is less than the air pressure inside a building

3. According to the passage, the pressure on a building during a tornado can be reduced by _____.

　 A. closing the windows 　　　　　　　　 B. opening the windows

　　C. using an electric fan 　　　　　　　　 D. making the roof and walls stron

You’d better examine your homework _______.

A. closely　　　　 B.close　　　　 C. closed　　　 D.closing

When asked ________ they needed most, the kids said they wanted to be loved.

A. what　　　　　 B. why　　　　　 C. whom　　　　 D. Which

Students should be able to think for themselves ____ just obeying teachers.

A. in case of　 B. besides C. except　 D. instead of

She ought to stop work; she has a headache because she ______ all day long.

　 A.has been reading　 B.had read　 C.is reading D.read

Her pale face suggested that she _________ and I suggested tha she ____________ to hospital at once.

A was; go　　　 B be;go 　 C be;went　　　 D was;went

Don' t try to persuade ynur boss ; he won ' t have the 　　　 of employing me -- a fresh student.

A. intention　　　 B. attention　　　　　 C. sense　　　　　 D. attraction

He admitted ____________ his best friend, Jack , __________ to make up for that.

A. betraying, determining　　　　　　 B. betraying, determined

C. to betray, determining　　　　　　 D. to betray, determined