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).

Choose and correct the wrong one: She wants a China pen friend. __________________
A   B C

It’s _________ to learn English. It’s interesting. (   )

A．difficult

B．easy

C．hardly

Be ________! Don’t climb the tree.（ ）

A．careful

B．care

This is our _______ friend, Lingling. ( )

A．China

B．Chinese

C．the USA