Every possible means ______ to prevent t

问题选择题

Every possible means ______ to prevent the air pollution, but the sky is still not clear.

A．has been used　

B．have been used

C．is used　

D．are used

答案

答案：A

题目分析：句意：每种可能的方式都被使用过来阻止空气污染，但是天空还是不清楚。Means是单复数同形的单词，因为这里被every修饰，所以means这里是单数，谓语用单数，排除BD，从but the sky is still not clear. 可知这里强调的是已经被使用了，用现在完成时，选A.