Everyone wants to reduce pollution. But pollution problem is as complicated as it is serious. It is complicated because much pollution is caused by things that benefit people. For example, exhaust from automobiles causes a large percentage of all air pollution. But automobiles provide transportation for millions of people. Factories discharge much of the material which pollutes the air and water, but factories give employment to a large number of people. Too much fertilizer or pesticide can ruin soil, but fertilizers and pesticide are important aids to the growing of crops. Thus, to end or reduce pollution immediately, people would have to stop using many things that benefit them. Most people do not want to do that, of course. But pollution can be gradually reduced in several ways.

Answer the questions:

Do factories discharge a lot of the material that pollutes the water?