Unit 9　Wheels

　　未来汽车的发展趋势是由大变小，小汽车的好处有多少？

　　Small cars

　　Here are two cars that may some day take the place of today's big automobiles.If everyone drives such a car in the future，there will be less pollution in the air.There will be more parking space in the cities，and the streets will be less crowded.Three such cars can fit in the space now needed for one car of the usual size.

　　The little cars will cost much less to own and to drive.Driving will be safer，too，as these little cars can go only 65 kilometers per hour.

　　The cars of the future will be fine for getting round a city，but they will not be useful for long trips.If the car is powered by electricity，it will have two batteries，one for the motor and one for the horn，signals，etc.Little cars which are powered by gasoline will go 450 kilometers before needing to stop for more gasoline.

　　If big cars are still used along with the small ones，two sets of roads will be needed in the future.Some roads will be used for the big，fast cars，and the other roads will be needed for the small，slower ones.

　　1．crowded adj.　　　　　 拥挤的

　　2．power vt. 提供动力

　　3．battery n. 电池

4．horn n. 喇叭