三、听短文，给下列图片排序。

  More and more people go to work by bus. Students go to school by bus. Some of their homes are not far from school. It takes them only ten minutes. But they don’t go by bike. They don’t like to walk. They don’t like to get up earlier. This brings a problem. There are more and more buses and cars. The air is not clean. This is not good for people’s health.