Mr. Green is said an experiment to prove the new method of solving　the problem when youn

发布时间：2020-08-17 15:07:48

Mr. Green is said      an experiment to prove the new method of solving　the problem when young.
A. to do
B. to have done
C. to be doing
D. to have been doing

网友回答

A. to do
(答案→)B. to have done
C. to be doing
D. to have been doing
解析：由when young可知此处应该用不定式的完成式。
以上问题属网友观点，不代表本站立场，仅供参考！