Man pollutes his environment in various ways. For example, some people dirty the air wiih gases and smoke. The machines and motor vehicles they operate fill the air with 1______ noise. 2______ people poison the water with chemicals and other 3______. Still others damage the soil with too many 4______.5______,people ruin natural beauty by 6______ rubbish on the land and in the water. Today, millions of people have become alarmed by the dangers of 7______, and large numbers of people are trying to reduce it.
But it is not easy to reduce pollution 8 much of it is caused by things that 9______ people. For example, exhaust from automobiles causes a large percentage of all air pollution, but the automobiles provide 10______ for millions of people. 11______ discharge much of the materials that 12______ air and water, but factories 13______ jobs for people. Too much chemical fertilizer can 14______ soil, but fertilizers are important 15______ to the growth of crops.
However, people have already found several ways in which pollution can be gradually 16______. Scientists and engineers have found some ways to 17______ the amount of pollution that 18______ things as automobiles and factories cause. Governments can pass laws that 19______ businesses and individuals to stop or reduce certain polluting 20______.
15
A.promoting
B.running
C.aids
D.lay
正确答案是C