运用临床现有的资料如病历进行分析和总结属于回顾性研究。()
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Delphi法是指选择一组专家,邀请他们就一份问卷进行评审,提出意见并进行修改,但缺点是各专家之间可能相互影响。()
Six out of ten prisoners in chains are black, which is ______ the chain gangs call up images of slavery in centuries gone by.
A. when
B. where
C. what
D. why
There happened to be some students in the room, ______?
A. didn"t they
B. didn"t there
C. doesn"t there
D. weren"t they