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