—It’snecessary

问题详情：

—It’s necessary ____ us ____ obey the traffic rules.

       —You’re right. Everyone has but only one life.

            A. for; to                  B. for; for                   C. to; to                        D. to; for

【回答】

A    It’s+adj. (+for sb. )+to do sth. 为固定句型。故选A。

知识点：介词和介词短语

题型：选择题