问题
选择题
If we had taken such effective measures much earlier, the river ________ 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：本句从句与过去的事实相反，而主句与现在的事实相反，这里now是解题关键。句意：如果我们早些采取如此有效的措施，这条河现在就不会被严重地污染了。根据句意选B。