There are more and more peolpe go out by bike.It is very popular in most of the cities for its convenience.Especially in such a crowd city as beijing.It will be more faster than being stopped in a heavy traffic jam.As for me,i will prefer bike than car.Not only because it can save money and for me and save energy but also it can avoid air pollution.The air condition is getting worse and worse,and i believe that it is everyone's duty to protect our environment.And also,it takes less space for us,which is a big advantage in city life.Although bicycle riding may make riders tired,it can keep your healthy at the same time.Compared with bikes,many people may say that cars can save time,so the high cost can be understood.But what about the air pollution it causes?I think nothing can be more important than protect the earth which is considered our only home.Car need more space to take,then it will be inconvenient to people to use the public space.To make a long story short,we should support bikes for our life's good.自己写的？