单项选择题

The upper atmosphere is believed to consist of a number of roughly concentric layers, which include the troposphere () and stratosphere ().

A. plainly
B. repeatedly
C. nearly
D. changeably
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单项选择题
Her death was a grief to him and I doubt if he ever recovered afterwards.
A. got by
B. got through
C. got on
D. got over
单项选择题
She could fix the machine without referring to the instructions.
A. understanding
B. observing
C. consulting
D. obtaining
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