问题
选择题
(2013·陕西师大附中模拟)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
选B 句意：如果我们早采取有力措施，现在河水就不会污染这么严重。主句表示与现在事实相反的虚拟语气，用would加动词原形。