单项选择题

They took ______ measures to prevent poisonous gases from escaping.

A. fruitful
B. beneficial
C. sufficient
D. effective
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______ is often more difficult to find trained men than to get financial support for scientific research.
A. It
B. That
C. This
D. What
单项选择题
The doctor advised that he ______ smoking immediately.
A. stops
B. stopped
C. stop
D. will stop
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