Ruby walks to school on school days. She thinks it is good for her health.

Julie goes to work by subway every day. She is never late for work.

Timmy goes to school in his father's car. He doesn't like to take the bus or ride a bike.

Jack likes travelling very much. He often goes to different places by plane.

Tom lives in a small village. He often goes out to the town by boat.

A. He likes doing exercise. He wants to keep healthy. So he often goes to work by bike.

B. He has a car. He wants to make his son happy so he often takes his son to school in his car.

C. She lives near a subway station. It's very convenient(方便的) for her to take the subway.

D. Her home is not far from her school. It takes her just 10 minutes to walk to school.

E. She lives very far from her work place. She needs to take a bus first and then walks 20 minutes to her work place.

F. There is no other vehicles except boats in his village. The villagers need to go out on boats.

G. His home is not far from the airport (飞机场). It just takes him 10 minutes to get to the airport from his home.

—He was late          his clock didn't work, not          the bad weather.

Each year the number of cars on roads and streets is becoming larger and larger. Millions of new cars are produced. One out of every six Americans works at putting together the parts of cars, driving trucks, building roads or filling cars with gas. Americans won't live without cars!

Most Americans find it hard to think what life would be without a car. However, some have realised the serious problem of air pollution caused by cars. The polluted air is poisonous and dangerous to health.

One way to reduce the polluted air is to build a new kind of car. Some large car factories are trying to do. But to build a clean car is easier said than done. It develops very slowly.

Another way is to take the place of the car engine (发动机) by something else. Engineers are now working on some new cars. It will take years to develop it.

To prevent the world from being polluted by cars, we'll have to make some changes in the way of life. Americans, for example, have to cut down the number of their cars. They are encouraged to travel and go to work by bike. Riding a bike is 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 closes down. And the problem of air pollution would become less important than that of unemployment (失业).

Although cars have brought us a better life, they have also brought us new problems.