二：语法和词汇知识（共20小题，每小题1分，满分20分）。6.we must keep in mind is that we must protect water and use

二：语法和词汇知识（共20小题，每小题1分，满分20分）。
6.    we must keep in mind is that we must protect water and use it wisely.
A. Why
B. What
C. Where
D. How