问题
You cannot take back your words _________ they are out of your mouth.
A:before
B:whether
C:once
D:while
B:whether
C:once
D:while
正确答案是：
同类题型
They ________ two free tickets to Canada.Otherwise，they’d never have been able to afford to go.
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No hurry at allThe train will come in an hour；________, we can have lunch
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