问题补充:
the task , they have to stay there for another two weeks.
A. Not completing
B. Not completed
C. Not having completed
D. Having not completed
答案:
A. Not completing
B. Not completed
(答案→)C. Not having completed
D. Having not completed
解析:考查现在分词的完成式做状语,因为他们是先没有完成任务,然后不得不在这儿再待两个星期。表示从句的动作先于主句的动作,要用现在分词的完成式,否定式是:not having done。选C。