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问题 多项选择题

病例对照研究在研究病因时主要缺点有（）

A.统计处理复杂

B.难以得到符合要求的对照

C.回忆偏倚大

D.时间顺序有时不清

E.一次只能研究有限的几个因素

答案

参考答案：C, D

选择题

— _    good time we had at the party last night!

— Yes. It was _____ exciting party that I would never forget it.

A．What; so

B．How; such

C．What a: such an

D．How a; so an
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选择题

He used to _____ being alone, but now he has grown up. [ ]

A. be afraid of

B. afraid of

C. be afraid to

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