单项选择题
在明确问题内容要点后进行实地调查，以便如实反映问题，是（ ）性调研。
A.
探索
B.
描述
C.
因果
D.
预测
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单项选择题
Which rank of study design correctly shows the strong to weak causal evidence ? A、Randomized controlled experiment, single-group time series experiment, multi-group time series experiment, no control before and after comparison experiment B、Randomized controlled trial, case-control study, case-control study nested in a cohort,ecological study C、Prospective cohort study, case-control study nested in a cohort, case-control study, cross-sectional study D、Historic cohort study, prospective cohort study, case-control study, cross-sectional study