thêm mở bài và kết bài cho cuộc hội thoại này. A: As you know, our enviroment is becoming worse and worse. What should we do to make the enviroment greener? B: In my opinion, we should plant a lot of trees. A: Planting trees? B: Yes, tree play an important role in our life. They provide us oxygen and get CO2 (carbon diocide). It makes our enviroment fresher. A: We also go to work by public transportor bike. If we do this, we can reduce pollution. B: It’s necessary to use 3Rs – reduce – reuse – recycle. A: Reduce? Can you explain more clearly? B:Oh! We should save our energy. Turn off the light when we don’t use them. A: And reuse? B: We can reuse bottles, boxes, books, and so on.