单项选择题

When our university laboratory bought this microscope we were given a one year's _______.

A．reservation
B．security
C．proof
D．guarantee
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单项选择题
The energy gained from the sun can then be used during the hight to enable the necessary chemi-cal reactions to _______ in his body.
A．conduct
B．proceed
C．progress
D．practice
单项选择题
The painter Jacob Lawrence frequently incorporated patterns into his compositions, making them more striking than they would _______ have been.
A．instead
B．however
C．otherwise
D．nevertheless
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