Every possibles means （ ）to prevent the air pollution,but the sky is still not clear.A.is used B.are used C.has been used D.have been used哪一个?为什么?
问题描述：
Every possibles means （ ）to prevent the air pollution,but the sky is still not clear.
A.is used B.are used C.has been used D.have been used
哪一个?为什么?
答
选C，强调个体，用单数
答
C
从句意看出是已经用过了,所以用完成时；因为前面是every,而means 单复同型,这里是单数,所以选C