This is not an economical way to get more water; it is very expensive.A. on the contraryB

问题补充：

This is not an economical way to get more water; ,it is very expensive.

A. on the contrary

B. on the other hand

C. in a word

D. rather than

答案：

(答案→)A. on the contrary

B. on the other hand

C. in a word

D. rather than

解析：本题的含义是这不是得到更多水的经济方式，相反，它的价格非常昂贵，on the contrary表示相反的意思，与题意较符合，故本题选A。