Pollution
①With the development of modern agriculture and industry, more and more waste is produced. Much of this waste is harmful. It goes into the water, the soil and the air. Some of it is absorbed and made harmless. But where there is too much of it, the poisonous waste may do great harm to the things around us
②When farmers add fertilizer(肥料) to the soil to make plants grow better, or spray(喷洒) poison to kill plant pests, poison is sent into the air, the water and the soil. When birds, fish and people eat the grain, drink the water or breathe the air, harm will be down to their health.
③The air in big cities is often made very dirty by factories. Millions of tons of waste ad poisonous gases are sent into the air with the smoke. In some places, little is done to make the smoke clean before it goes into the air.
④Oil is burnt in cars, trucks and buses. They produce waste gases almost as harmful as the gases from factories. In big cities during cold winter months, many old people die from the polluted air. In places around big factories, trees and vegetables are often killed by the bad air.
⑤Another kind of pollution is noise. Very loud noises can make people ill, hurt their ears, or even drive them mad. Houses near airports sometimes have their windows broken by the noise of jet planes passing overhead. Workers in some industries have their hearing harmed by the noise of the machines.
前5道题选项：
A. Traffic Jam
B. Dirty Air in Big Cities
C. Harmful Waste
D. Noise Pollution
E. Soil Pollution
F. Air Pollution
后5道题选项：
A. workers’ hearing
B. the polluted air
C. burning oil
D. help the growth of plants
E. keep people health
F. more and more waste

Cars, trucks and buses produce waste gases because of _________.