No matter how hard he worked,
A. he could not do any better
B. and he could not do any better
C. so he could not do any better
D. but he could not do any better
网友回答
(答案→)A. he could not do any better
B. and he could not do any better
C. so he could not do any better
D. but he could not do any better
解析：可联系答.案.网客服索取。