I recommended an English-Chinese dictionary which I thought would be of great help to hi

问题补充：

I recommended an English-Chinese dictionary, which I thought would be of great help to his studies.

A. him buy

B. he bought

C. to buy

D. buying

答案：

A. him buy

B. he bought

C. to buy

(答案→)D. buying

解析：可联系答.案.网客服索取。