Ken is my friend. He ____ (come) from London, UK. Five years ago I ____(meet) him at Lily's party. Then we ____ (become) good friends. Ken and I ____ (reach) Washington D.C. at the same time. We____ (start) to study medicine in the same school. Now we are still studying together. So I know more about him. Ken is funny He often ____ (make) up some interesting stories to make me laugh. He says he's not going to be a doctor when he graduates (毕业). He ____ (want) to be an actor. He ____ (take) acting lessons when he is free. He ____ (make) lots of funny movies to make people happy. I believe his dream ____ (come) true.

下列做法对环境保护有利的是（  ）