I think is necessary us to do something useful to protect the birds.A．this; forB．it; o

题目简介

I think ______ is necessary ______ us to do something useful to protect the birds.A．this; forB．it; o

I think ______ is necessary ______ us to do something useful to protect the birds.

A．this; for

B．it; of

C．this; of

D．it;for

题型：单选题难度：偏易来源：不详

考查固定句型。It is+形容词+for sb. to do sth.句中it作形式主语。