阅读下面三篇短文，根据短文内容，从所给的A、B、C、D四个选项中选出最佳选项。

C

    I live in a town. In the past, the air wasn't fresh. There was a river. People put rubbish in it. The water went bad. The fishes in the river died. There was much rubbish in the streets which weren't wide. It smelt terrible. People lived in low old houses with trees all around and had a terrible life. The children couldn't have many chances to go out to cities, not to say, have a good education. Farmers worked only with their hands. They worked very hard all year round. They planted crops(农作物)with the help of animals. The poor people went anywhere on foot, and only some rode bikes. Few visitors came here to spend their holidays.

    At present, things have been greatly changed. People have moved into big bright houses or beautiful buildings. There is a big factory. Many people work in it. They are getting richer. Different kinds of cars and buses are running in the big streets. It is faster and easier to travel. People plant many fruit trees and get much money. People plant crops with the help of machines which can save lots of work. Students can study in a modem school. People pay more attention to the environmental protection. The mountains are becoming greener, water much cleaner. What around us is the clearer sky and greener water. As a result, many visitors come here to spend their holidays. People enjoy their modern life. But with the development of the industry, we have fewer trees. Air and water pollution is becoming more and more serious. We must do something to stop pollution to make our town more and more beautiful.