He failed in the English speech contest he did his best to prepare for it.A. thoughB. bu

问题补充：

He failed in the English speech contest, he did his best to prepare for it.

A. though

B. but

C. because

D. so

答案：

A. though

(答案→)B. but

C. because

D. so

解析：题中句意，转折应用but