He tried his best to solve the problem, difficult it was.A. howeverB. no matterC. whateve

发布时间：2020-08-16 16:46:08

He tried his best to solve the problem,      difficult it was.
A. however
B. no matter
C. whatever
D. although

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(答案→)A. however
B. no matter
C. whatever
D. although
解析：四个选项分别表示然而可是、不论怎样、无论什么和尽管，根据题意选A，他尽了最大努力解决问题，可是困难依旧。
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