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
Because Edgar was convinced of the accuracy of this fact, he ______ his opinion.
A．struck at
B．strove for
C．stuck to
D．stood for
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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