I always regret notharder when I was young .A. studyingB. having studiedC. to studyD. to h

问题补充：

I always regret notharder when I was young .

A. studying

B. having studied

C. to study

D. to have studied

答案：

A. studying

(答案→)B. having studied

C. to study

D. to have studied

解析：考查非谓语动词。句意“我这是后悔年轻的时候没有好好学习。”regret doing sth.“后悔做了某事”；regret to do sth.“后悔要做某事”。根据句意是已经发生的事情，排除C、D；根据when从句可知，是后悔过去的事情，已经用完成时。故选B。