Do you know you could get sick just by walking past a building? The bacteria(细菌) that cause Legionnaire's disease grow very fast in large modern buildings. They are carried by air through the buildings and outside. Legionnaire s disease is only one of the illnesses that are caused by "sick buildings".
Some buildings can make you ill because their heating and air-conditioning(空调调节系统) are controlled(控制). Air from outside cannot get in through the closed windows; This indoor air pollution is a growing problem.
Legionnaire's disease may be the most serious result of sick buildings, but other unpleasant illnesses can appear.People who work in some buildings suffer （受苦）from tiredness, feeling sick and headaches. Their offices look bright and clean, but invisible(无形的) and dangerous bacteria are in the air around them.
There is an answer to the problem. The air-conditioning and heating can be tested for bacteria. Once the tests are finished, the sick buildings can be cured. This is expensive to do, but the results are good. The people in the buildings no longer get sick, and everybody is happier.
"Sick buildings" means _______.

A．very old buildings

B．buildings that make people feel sick

C．buildings for sick people

D．buildings that are going to fall down

The indoor air pollution is caused by _______.

A．Legionnaire's disease	B．the air from outside
C．lack(缺乏) of fresh air	D．unpleasant illnesses

We can tell that a building might be "sick" when _______.

A．the windows are all closed

B．bacteria can be seen in the air

C．the air-conditioning and heating don't work well

D．people in it have got different kinds of diseases

Which of the following is TRUE?

A．Legionnaire's disease is only one of the results of "sick buildings".

B．There is less and less indoor air pollution.

C．The bacteria are not dangerous if the offices look bright and clean.

D．If the tests for bacteria are expensive. the results are good. .

The underlined sentence in the last paragraph means "As soon as the tests are finished, _______."

A．bacteria will disappear by themselves

B．Legionnaire's disease won't kill people

C．people in the building will no longer get sick

D．something can be done to cure the sick building