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).