each year there is an increasing number of cars on the roads as millions of new cars are produced. one out of six americans works at making cars, driving trucks, building roads or filling up gas. americans couldn`t live without cars!
most americans would find it hard to imagine life without a car. however, some have realized the serious problem of air pollution caused by cars. the polluted air becomes poisonous and dangerous to health.
one way to get rid of the polluted air is to make a car without pollution. but to build a clean car is easier said than done. progress in this field is slow.
another way is to replace car engines with something else. inventors are now working on steam cars as well as electric cars. many makers believe that it will take years to develop a practical model for us.
to prevent the world from being polluted by cars, we have to make some changes in our lives. americans, for example, have to cut down on the number of their total cars.they are encouraged to use bicycles, which are thought to help keep the air clean.
but this change does not come easily. a large number of workers may find themselves without jobs if a car factory cioses down. thus the problem of air pollution would become less important than that of unemployment. although cars have led us to a better life, they have also brought us new problems.
来源：作文地带整理。
