No matter how hard he worked, _______．
A.he could not do any betterB.and he could not do any betterC.so he could do any betterD.but he could not do any better在线课程A
由no matter引导的让步状语从句，其主句也不能再用but，and，so 等并列连接词，即它已经引导了一个状语从句。