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 has been estimated that the earth's surface temperature has increased ______ one quarter to three quarters of a degree since 1850. ~
A．to
B．by
C．at
D．with
单项选择题
The prisoner has been ______ of many privileges that average citizens enjoy.
A．ensured
B．informed
C．deprived
D．convinced
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