Rita studies in a big city. She knows that pollution is a big problem. The big city is very crowded. The streets are filled with cars. Some people don't like this. They say that the air is too dirty because of so many cars. It is not good to live in the city with it. Rita has a good idea. She says，"When I grow up, I will be a big bus to go to work and go back home again." Yes, that's a good idea. If people take the girl's bus, the air will be cleaner than now.