(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.