皮皮学，免费搜题
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【单选题】
蛋白质分子中维持一级结构的主要化学键是A.
二硫键
B.
肽键
C.
氢键
D.
次极键
E.
以上都不对
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知识点：
皮皮学刷刷变学霸
举一反三
【单选题】They had no sooner arrived at the airport ________ it was time to check in. [ ]
A.
when
B.
before
C.
than
D.
though
【单选题】Which of the following contains an adverbial clause of time?
A.
No sooner had I got home than it began to rain.
B.
I do remember, now that you mention it.
C.
You'll be late unless you hurry.
D.
Much as I'd like to, I can't come.
【单选题】No sooner _______ the competition _______ _______ an unexpected accident happened.
A.
did … begin; than
B.
had … begun; when
C.
did … begin; when
D.
had … begun; than
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