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【单选题】
实验性研究不包括:A.
主要在现场进行
B.
在人群中观察某项预防措施的效果
C.
在临床上观察某种新药或新疗法的疗效
D.
先选病例,再探索其暴露因素
E.
盲法研究
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A.
The amount and quality of sleep.
B.
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C.
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D.
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【单选题】—Keep quiet, kids. Dad ______ in the next room. —OK, Mum. [ ]
A.
is sleeping
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D.
sleeps
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