Question

【题目】__________ the task, they had to stay in the lab for another two hours.

A. Not completing B. Not completed

C. Not having completed D. Having not completed

Answer 1

【答案】C

【解析】C 句意：由于还没有完成任务，他们不得不在实验室再待两个小时。动词-ing形式的完成式表示动作发生在had to stay in the tab for another two hours 之前，其否定形式是在动词-ing之前加not。