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
______it is you' re found, you must give it back to the person it belongs to.
A．That
B．Because
C．Whatever
D．However
单项选择题
The pollution question as well as several other issues is going to be discussed when the Congress is in ______again next spring.
A．assembly
B．session
C．conference
D．convention
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