题目内容：

Air pollution is one of the hottest topics at present because poor air quality is an important factor in both the incidence and cause of respiratory(呼吸道) diseases.

Zhong Nanshan, a deputy to the NPC and a member of the CAE, said recently when the concentration of PM2.5 rises by 10 micrograms per cubic meter, hospitalization may rise by as much as 3.1 percent. Meanwhile, when the concentration of PM2.5 rises from 25 mgs per cubic meter to 200, the average daily death rate may rise to 11 percent.

Zhi Xiuyi, a leading expert in lung cancer treatment and also vice-president of the CATS, said medical authorities used to focus on tobacco control as a primary means of preventing lung cancer. "But in fact, air pollution is no less harmful than smoking and our research team released a report earlier this year showing that the cancer rate in Beijing is closely related to industrialization," he said.

The report, conducted by the Beijing Institute of Cancer Research, shows that the number of cancer patients in China has increased markedly during the past ten years. Chaoyang District, the city's main area of industrialization, has the highest incidence of cancer, almost double that of Yanqing, an area on the outskirts of the city. About four out of 1000 Chaoyang residents have some form of the disease, with lung cancer at the top of the list.

"The risk of having cancer largely depends on the length of exposure and the concentration of noxious gases(有毒气体的浓度)," said Zhi. In response to the doubt whether seven years' exposure to poor air quality will almost result in cancer, Zhi said the time scale was taken from research overseas that suggested the rate of incidence generally peaked in the seventh year of exposure to a heavily polluted environment.

1. What is the passage mainly about?

A. Medical researches on environment.

B. The disadvantages in big cities.

C. The only reason for the lung cancer.

D. Poor air quality contributing to lung cancer.

2.What can you conclude from the 3rd paragraph?

A. Compared with smoking, air pollution is more harmful.

B. Air pollution is as harmful as smoking.

C. It is very important to prevent people from smoking.

D. People realize the importance of keeping healthy.

3.If there were 3,000,000 people in Chaoyang District, how many would have respiratory diseases?

A. 16000       B. 12000       C. 8000        D. 7500

4.What can you infer from the passage?

A. Industrialization has its weakness as well as strengths.

B. The average death rate rises with different ages and places.

C. The air in Beijing is much more polluted than that in the other cities.

D. The more heavily-polluted air you breathe in, the sooner you’ll have cancer.