Not until World War II ______ to use new chemical techniques to purify penicilli

题干

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

上一题下一题 0.64难度单项选择更新时间:2013-06-06 04:00:56

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