单项选择题

A．If they don’t involve any risks.
B．If they produce predictable side effects.
C．When the urgent need for them arises.
D．When tests show that .they are relatively safe.
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单项选择题
A．Classmates.B．Colleagues.C．Boss and secretary.D．PR representative and client.
A．Classmates.
B．Colleagues.
C．Boss and secretary.
D．PR representative and client.
单项选择题
A．By greeting each other very politely.B．By exchanging their views on public affairs.C．By displaying their feelings and emotions.D．By asking each other some personal questions.
A．By greeting each other very politely.
B．By exchanging their views on public affairs.
C．By displaying their feelings and emotions.
D．By asking each other some personal questions.
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