问题
选择题
—Why does the lake smell terrible?
—Because large quantities of water _____.
A．have polluted.
B．is being polluted.
C．has been polluted.
D．have been polluted.
答案
答案：D
题目分析：从问句和答语可知说的是湖的现在的情况，又因为强调污染对湖所产生了一定的结果和影响，故在C，D中选择正确答案。由于主语是quantities，谓语动词要用复数。故选D。
点评：熟练掌握现在完成时和名词的主谓一致中一些需要记忆的知识点。