Read the below conversation.  Li Ming: What are you doing, Mum?  Mum: I'm getting something ready for tomorrow. Tomorrow is Tre e-planting Day.  Li Ming: Tree-planting Day? What do people do on this day, Mum?  Mum: Many, many people will go and plant trees.  Li Ming: Why do they do tha t?  Mum: To make the earth more beautiful. And to make our life better.  Li Ming: But I often see people on TV cut down many big trees. Why do they do that, Mum?  Mum: Hm, to make paper, houses, and to make our life better.  Li Ming: To make our life better, too? I just don't understand. Mum, why do many people go and plant trees on the same day?  What would the listener say?

Mum: Oh, my dear son. It's hard to explain to you. When you grow up, you will understand. Just remember trees are very important to us.