He tried his best to solve the problem,however difficult it

He tried his best to solve the problem,however difficult it He tried his best to solve the problem,______ difficult it w He tried his best to solve the problem,_______difficult it w He tried his best to solve the problem __difficult it was 为什 ___difficult the problem was,he tried his best to solve it. 帮我检查:He tried his best to solve the problem,( ) He tried his best to slove the problem,_A___difficult it was The determined boy tried his best to solve the problem,_____ but he found the problem difficult to solve we had to___ to solve the maths problem A .tried our best B. we had to___ to solve the maths problem A.tried our best B.t Tough he tried many ways to solve the problem,______worked;h