【题目】They failed to finish the project in time. I regretted _________ them.
A. to be not able to help B. being not able to help
C. not being able to help D. not be able to help
在线课程【答案】C
【解析】考查动名词。 regret doing "遗憾做了某事" 跟动名词；regret to do sth.遗憾地去做某事。句意：他们没有按时完成项目,我非常遗憾没能帮上他们的忙。动名词的否定形式 not doing
所以选C。