用所给单词的适当形式填空。
【小题1】Water is very________(use).
【小题2】We use wood________(make) chairs.
【小题3】Trees help________(keep) the air clean.
【小题4】________(protect) the Earth, we should________(save) water.
【小题5】Look! They________(do) a project.
【小题6】Please tell________(they) about Christmas.
【小题7】He starts________(sing).

The Chinese people____gunpowder in the 9^th century.

A．discovered

B．discover

C．will discover

The sun _______ .（ ）

A．rises

B．rise

C．rising

We are rabbits. We  a new flat.

A．have

B．has

写出下列单词的-ing形式。
1.sing  ______________
2.do ______________
3.dance  ______________
4.swim______________
5.shop   ______________