国家开放大学 / 综合英语（3）
正确率：100%
The researchers have conducted an experiment to prove that people will act in emergencies when _ _ _ _ _ _ _ .
A.they are in pairs
B.they are in groups
C.they are alone
D.they are with their friends
A.they are in pairs
B.they are in groups
C.they are alone
D.they are with their friends
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