单项选择题

According to the passage, the first maser was built probably in______.

A.1917
B.1951
C.1957
D.1953
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单项选择题
In his research at Columbia University Charles Townes worked with all of the following EXCEPT______.
A.stimulated
B.amplification
C.microwaves
D.a maser
单项选择题
People seldom feel neutral about poetry (in Para. 1) in this context means that______.
A.few people think that poetry is neutral
B.people always differ in their views about poetry
C.people rarely take a biased opinion about poetry
D.people generally think of poetry as extremely important or totally useless
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