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
I bought a large Chinese ______ lampshade to put in my bedroom.
A．old
B．round
C．white
D．paper
单项选择题
In vain ______ to get in touch with the Embassy.
A．they tried
B．tried they
C．did they try
D．they have tried
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