In the eyes of many people, city is attractive with all its advantages and conveniences. People can buy almost all kinds of things at supermarkets or shopping malls, dine out in good restaurant, they can have more educational opportunities. However, with the expansion the city, more and more people are flowing into the big city. Now the traffic is heavier and heavier. The pollution problem is getting more and more serious. The living condition is worse and worse. Most people love the advantages of city life, but a big city also has its disadvantages.