More and more people have come to realiz

问题选择题

More and more people have come to realize that if we had taken effective measures much earlier, the air quality ______ so seriously now.

A．is not polluted

B．would not be polluted

C．had not been polluted

D．would not have been polluted

答案

答案：B

题目分析：句意，越来越多的人意识到如果我们早点采取有效地措施，现在空气污染就不会这么严重了。If条件从句是对过去的虚拟，故用过去完成时，而主句是对现在的虚拟，故用would do形式。

点评：所谓错综时间条件句即条件从句与主句所指时间不一致，如从句指过去，而主句即指的是现在或将来，此时应根据具体的语境情况，主、从句动词的形式应根据各自所表示的时间进行调整。