Only after he had spent several nights working on the math problem _______ to wonder whether the problem was wrongly set.
A.that he began | B.did he begin | C.then he began | D.so that he began |
推荐套卷
Only after he had spent several nights working on the math problem _______ to wonder whether the problem was wrongly set.
A.that he began | B.did he begin | C.then he began | D.so that he began |