--We could have asked Mr. Zhang for help. He is caring and considerate.--I that. A

问题补充：

----- We could have asked Mr. Zhang for help. He is caring and considerate.

----- I that. A long time .

A. forgot; had been wasted

B. forget; wasted

C. have forgotten; wastes

D. forgot; was wasted

答案：

A. forgot; had been wasted

B. forget; wasted

C. have forgotten; wastes

(答案→)D. forgot; was wasted

解析：考查时态语态：句意是;--我们本来是可以向张先生求助的，他很有爱心也考虑周到。--我忘了，那么长时间被浪费了。说明忘了是过去发生的，时间也被浪费了。选D。