6 -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 [解析]D考查动词时态.语态和主谓语一致.根据前一分句可知所填动词表示过去发生的动作对现在产生的影响.时态用现在完成时.动词与主语是被动关系.用被动语态.主语是large quantities of water.其中心词是quantities.是复数.谓语动词用复数.选D. 【查看更多】
