单选题 People have worried about smog for many years, and the government has spent billions of dollars to try to clean up the air of big cities. Now we find that there is no escape from unhealthful air. Recent studies have shown that air inside many homes, office buildings, and schools is full of pollutants; chemicals, bacteria, smoke, and gases. These pollutants are causing a group of unpleasant and dangerous symptoms that experts call "sick building syndrome". A "sick building" might be a small house in a rural area or an enormous office building in an urban center. A recent study reached a surprising conclusion: Indoor air pollution is almost always two to five times worse than outside pollution! This is true even in buildings that are close to factories that produce chemicals. The solution to this problem would seem very clear; Open your windows and stay out of modern office buildings with windows that don't open. Unfortunately, the solution might not be so simple, better ventilation—a system for moving fresh air—can cut indoor air pollution to a safe level, but lack of ventilation is seldom the main cause of the problem. Experts have found that buildings create their own pollution. Imagine a typical home. The people who live there burn oil, wood, or gas for cooking and heating. They might smoke cigarettes, pipes, or cigars. They use chemicals for cleaning. They use hundreds of products made of plastic or particle board; these products—such as the shelves in Oakland High School— give off chemicals that we can' t see but that we do breathe in. And in many areas, the ground under the building might send a dangerous gas called radon into the home. The people in the house are breathing in a "chemical soup" , and medical experts don't yet know how dangerous this is for the human body.

单选题 In the first paragraph the author is trying to draw our attention______.

单选题 From the passage, we know the author' s solution to the problem of "sick building syndrome" is______.

单选题 The reason why the problem can not be eradicated is that______.

单选题 According to the passage, which of the following is true of "sick building syndrome"?

单选题 Which of the following statements can be concluded from the passage?