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。

A: The spring has already come. The weather is getting warmer and warmer. More and more

    people like to go to the park to have a picnic.

B: So they do. But after they leave, (1)_______________.

A: We should do something to keep it clean.

B: That sounds good. First we need to (2)_______________ some ideas.

A: While we talk, I'll write down all our ideas.

B: We must put up some signs to tell people (3)_______________.

A: But many people don't care about what the signs say and always throw about the litter.

B: (4)_______________?

A: It's a good idea, but only you and me?

B: OK, we each call up ten people and ask them to help pick.

A: Wonderful. I'm sure our parents will take (5)_______________ in us.

B: I think so. But let's have lunch first.  I'm too hungry.