单项选择题

The invisible rays of the ______ beyond the violet end are called the ultraviolet rays.

A．speculation
B．spectrum
C．sleet
D．range
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单项选择题
In his ______ to further his knowledge of the universe, man has now begun to explore space.
A．endeavor
B．expedition
C．trail
D．chase
单项选择题
It is always useful to have savings to ______.
A．come out in
B．live up to
C．make a fuss of
D．fall back on
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