单项选择题

Recently, great advances have been made in the study of Mars' surface by the use of radar waves to ______ the dense cloud layer.

A．hover
B．pierce
C．penetrate
D．plunge
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单项选择题
The passage is mainly about ______.
A．generation gap
B．establishment and authority
C．the young and their ambition
D．reward according to ability not according to age
单项选择题
The author seems to be in favor of ______.
A．the old
B．the young
C．the authority
D．the Establishment
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