__________,they provide a rapid means of getting information about many people.A.Properly be used B.Properly used C.If u
问题描述：
__________,they provide a rapid means of getting information about many people.A.Properly be used B.Properly used C.If use it properly D.Been properly used 原因要讲清楚
答
选c.这里面省略了主语They,因为后面有they,所以可以省略.然而一个句子不能有两个动词,所以A不选.B中把他省略的东西补上就是It is properly used.主语是it 与后面的主语不一样,不能省.没有D这种用法