问题:
Not until World War II ______ to use new chemical techniques to purify penicillin.
A.they managed
B.that they managed
C.did they manage
D.they didn’t manage
Not until World War II ______ to use new chemical techniques to purify penicillin.
A.they managed | B.that they managed |
C.did they manage | D.they didn’t manage |
参考答案: