根据对话内容，在空白处填写适当的话语（话语可能是一个句子，也可能是一个短语或一个词）。使对话完整。
(Dan and Kate are talking about pollution.)
Dan: It is said that pollution is worse than before.
Kate: Yes, I have noticed this. What do you think of pollution?
Dan: It makes me a little worried. 1 ?
Kate: Me too. I think pollution is everyone's problem and it is everyone's duty to protect environment.
Dan: Quite right! But as a teenager, 2 ?
Kate: To start with, we should start a clean-up club. We can give out ads after school to tell people how
important environment is.
Dan: 3 !Besides this, we should make people know that pollution is the biggest challenge that they are
facing.
Kate: I agree with you. If everyone can do something to keep our environment clean, our world will be
4 .
Dan: Yes. As the saying goes. One finger cannot lift a small stone.
Dan: What else?
Kate: We shouldn't throw 5 everywhere, either.
Dan: OK. I'm sure we will be successful.
