He tried his best to solve the problem,______ difficult it wasA.however B.no matter C.whatever D.although请问答案是A,请问别的为什么不行?

He tried and tried his very best not to join in. tried ang tired his very best not to和surely if he really tried He tried his best to find a p___ word to express his feelings. He tried his best-[not show]it. he tried his best to make his classes live有一处错误, He tried his best to quit smoking but he failed.这个句子对吗?为什么 he tried his best to save the drown girl,but unfortunately she died.改错 Though Nick tried his best to play tennis,he played very________(bad)谢谢 Though Nick tried his best to play tennis,he piayed very _______(bad) Busy ( ) he was,he tried his best to help you.A.as B.when C.since D.for he is a little weak in this but he tried his best to catch up with other He is a little weak in this ,but he has tried his best to catch up with others. 什么意思 10.Busy _____ he was,he tried his best to help you.A.as B.when C.since D.for try one's best同义词He tried his best to help us.He ( ) ( )he could to help us可以讲下原因么， He tried his best in the race.翻译 帮我检查:He tried his best to solve the problem,( )帮我检查:He tried his best to solve the problem,( )difficult it was.a.howeverb.no matterc.whateverd.although ___difficult the problem was,he tried his best to solve it.A.No matter B.Although C.Whatever D.However he tried his best not to be influenced by the opinions that (围绕) him.括号里填什么?