第二卷 （共30分）
第四部分: 短文填空
阅读短文，根据所读内容在文后的空格里填上适当的单词。
With the (1) ____________ (develop) of industry, air pollution is getting more and more serious. In Beijing, many people suffer different kinds of illnesses because of air pollution.
Air pollution is caused by the following reasons: about half of the problem is caused by vehicles. There are more and more cars, buses on the roads, and they give off (2) __________ (poison) gases. 25% of air pollution is caused by factories. Another factor is the smokers. Smoking not only does harm to their health but also to others. (3) _________ these, about 10% of air pollution is caused by other reasons.
