Even a drop of water because it is so important to all the living things.A. must wasteB. m

问题补充：

Even a drop of water because it is so important to all the living things.

A. must waste

B. must be wasted

C. mustn’t waste

D. mustn’t be wasted

答案：

A. must waste

B. must be wasted

C. mustn’t waste

(答案→)D. mustn’t be wasted

解析：

这题考查情态动词的被动语态的用法，“情态动词+be+done”，句意是：一滴水都不能浪费，因为它对每个生物都是有用的，注意用否定式。