The thick smog covered the whole city.It was as if a great black blanket ______ over it.
问题描述：
The thick smog covered the whole city.It was as if a great black blanket ______ over it.
A.had been thrown B.were thrown
C.be thrown D.had thrown
主语说的不是现在的事实吗?不理解为什么要用到过去完成时.
答
as if 表示“好像”的意思,需要用虚拟