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．The long wait.B．The broken-down computer.C．The mistakes in her telephone bill.D．The bad telephone service.
A．The long wait.
B．The broken-down computer.
C．The mistakes in her telephone bill.
D．The bad telephone service.
单项选择题
A．He didn’t understand the lecture.B．He wants to borrow her notes next week.C．He heeds help with a makeup exam.D．He was sick and unable to attend.
A．He didn’t understand the lecture.
B．He wants to borrow her notes next week.
C．He heeds help with a makeup exam.
D．He was sick and unable to attend.
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