With the (31)_____________ (develop) of industry, air pollution is getting more  and more serious. In Beijing, many people (32)___________(suffering) from different kinds of (33) ___________ ( ill ) because of air pollution.
Air pollution is caused (34)_________ the following reasons: about half of the problem is caused by vehicles（车辆）. There are more and more cars, buses on the roads, and they give off (35)_________ (poison) gases. 25% of air pollution is caused by factories. Another (36)_________ (fact) is the smokers. Smoking not only does harm to their health but also to others’. (37)__________ these, about 10% of air pollution is caused by other reasons.   
We should take some measures to fight (38)_____________ pollution. New fuel can be used to take the place of gas. We can plant more trees. If everybody realizes the importance of (39)___________(environment) protection and does something to stop pollution, the problem will (40)___________(solve).