题目

Each year there is an increasing number of cars on roads and streets as millions of new cars and trucks are produced. One out of every six Americans works at putting together the parts of cars, driving trucks, building roads or filling cars and trucks with gas. American won’t live without cars! Most Americans would find it hard to think what life would look like without cars. However, some have realized the serious problem of the air pollution that is caused by the car. The polluted air becomes poisonous and dangerous to health. One way to get rid of the polluted air is to build a ca