用所给词的正确形式填空。
【小题1】We should stop _________ (throw) rubbish into rivers.
【小题2】In the past, the Earth _________ (be) clean and beautiful.
【小题3】My brother is __________ (plant) trees in the backyard.
【小题4】The Earth __________(get) sick now.
【小题5】We shouldn’t __________ (cut) down so many trees.

-- What are you doing in the park? -- I’m looking at the children ______ volleyball.

A．plays

B．playing

C．are playing

D．to play

用括号中所给单词的正确形式填空。
1. We can see some ________(snowman) in winter.
2. ________(one), I brush my teeth.
3. I have two sticks for his ________(arm).
4. Can you ________(put)it on the chair?
5. He is ________(clean)the room.

Some of the boys enjoy ______ football.

A．play

B．playing

C．to play

D．played

Five girls are ___________ the high jump. (    )

A．doing

B．does

C．do

D．to do