单项选择题

Frequent exposure to X-ray is harmful, so the use of X-ray should be limited to occasions when________.

A．primary
B．elementary
C．necessary
D．emergent
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单项选择题
The New York Times has ________ in France, Germany, and other countries.
A．reporters
B．journalists
C．announcers
D．correspondents
单项选择题
He put in a special ________ for an extra day's holiday so that he could attend his daughter's wedding.
A．request
B．requirement
C．demand
D．enquiry
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