问题
选择题
A number of tests have been conducted to _________ that these drugs have no side effects.
A．find out
B．look for
C．make sure
D．work out
答案
答案：C
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A number of tests have been conducted to _________ that these drugs have no side effects.
A．find out
B．look for
C．make sure
D．work out
答案：C