Most Americans would find it hard to think that what life 小题1:
would look like without a car. But, some have realized 小题2:
the serious question of the pollution caused by the car. 小题3:
The polluted air becomes harmful and dangerous to health 小题4:
One way to getting rid of the polluted air is to build a 小题5:
car that doesn’t cause pollution. That is how several of the 小题6:
large car factories have been tried to do. But to build 小题7:
a clean car is more easier said than done. Progress in this 小题8:
field has been slow.
Another way is to take place of the car engine by a 小题9:
steam one. Inventors are now working on steam cars as well as
electric cars. Many makers believe that it will spend 小题10:
years to develop a practical model that pleased people