题目是：

The earth is our home. We must take care of it. That is to say we must keep the land, air and ___1___ clean.
(    D  ) 1. A. river
B. sea
C. lake
D. water
     我选D.但正确答案是C. 哪位老师能解析一下吗？

land, air 和water是并列关系   river  sea和 lake是并列关系

land, air 和water是并列关系   river  sea和 lake是并列关系

楼主分析得有一定的道理哦。