It was playing computer games that cost the boy plenty of time that he spent doing his le

问题补充：

It was playing computer games that cost the boy plenty of time that he spent doing his lessons.

A. might have

B. should

C. ought to have

D. could

答案：

A. might have

B. should

(答案→)C. ought to have

D. could

解析：考查情态动词。根据句子，指的是过去的情况，所以要用情态动词加完成时态表过去本应该做而实际没做的事。might have done,本可以做某事；ought to have done本应该做而实际没做。句意：玩电脑游戏花费了这个男孩大量的时间，他本应该把时间用在功课上。所以选C。