In China, more and more people own private cars. It is said that in Guangzhou there are more than four hundred thousand cars. It's because the economy is expanding rapidly and therefore the family income goes up year by year. People want to enjoy a more comfortable life and earn certain social status. Private cars are one of their choices. There is no doubt that private cars make us travel faster and farther, but they do have caused some problems. For example, they emit too much ex ... ...