单项选择题

We must______ that the experiment is controlled as rigidly as possible.

A．secure
B．ensure
C．assure
D．issue
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单项选择题
The people at the party were worried about Susan because no one was aware______ she had gone.
A．where that
B．of where
C．the place where
D．the place
单项选择题
At no time______ other countries.
A．China will invade
B．will invade China
C．will China invade
D．invade will China
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