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
Although he refused to act on my suggestion, he had to admit that______ what I said.
A．it was something in
B．there was something in
C．it was something as for
D．there was something upon
单项选择题
After______ seemed an endless night, it was time for them to open the boxes of presents.
A．it
B．that
C．what
D．there
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