66. In the first paragraph the author is trying to draw our attention ____.

1. to the improved quality of outdoor air
2. to the risks of unhealthy air
3. to the sources of pollutants
4. to indoor pollution

67. From the passage, we know the author's solution to the problem of "sick building syndrome" is ____.

1. to build small houses in the rural areas
2. to live in buildings far from factories
3. to leave open the windows of the office where one works
4. to pull down all "sick buildings"

68. The reason why the problem cannot be eradicated is that ____.

1. there is lack of ventilation
2. it is caused by buildings themselves
3. it might not be simple
4. indoor air pollution cannot be improved through ventilation

69. According to the passage, which of the following is true of "sick building syndrome"?

1. All people can be ill when they breathe in indoor air with harmful ingredients.
2. Only old buildings can make people sick.
3. Outdoor air pollution is no less than indoor air pollution.
4. One shouldn't stay in the house where some people are seriously sick.

70. Which of the following statements can be concluded from the passage?

1. Sick building syndrome is a sort of disease that is incurable.
2. There is no air pollution in modern office buildings.
3. Few people have realized the danger and harm of indoor air pollution.
4. Chemicals should not be allowed to be produced so as to avoid sick building syndrome.

(Reference keys.)