阅读下面材料，在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。
With the   (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   (follow) reasons. It is  (main) caused by vehicles. There are more and more cars, buses on the roads and they give off   (poison) gases. About 25% of air pollution is caused by factories.  Another factor is the smoking,    not only does harm to smokers’ health but also to others’.   these, about 10% of air pollution is caused by other reasons.
We should take some measures  ( fight) against pollution. New fuel can be used to take   place of gas. We can plant more trees. If everyone realizes the importance of environment  does something to stop pollution, the problem will   (solve).