With the __________ （develop）of industry, air pollution is getting more and more serious. In Beijing, many people suffer different kinds of illnesses because _________ air pollution. Air pollution is caused by the following_________: about half of the problem is caused by vehicles. There are more and more cars, buses on the roads, and they give off _________( poison) gases. 25% of air pollution is caused by factories. Another factor is the smokers. Smoking not only does harm to their health ________ to others._________ these, about 10% of air pollution is caused by other reasons. We should take some measures to fight _________ pollution. New fuel can be used to take _________ place of gas. We can plant more trees. If everybody realizes the ________（important）of environment and does something to stop pollution, the problem will__________（solve）.