题目内容

以下有关前后对照试验的描述，错误的是：（）

A. 比较节省研究样本量
B. 可以采用随机的方法决定试验药物和对照药物的先后顺序
C. 将试验药物使用前后的效果进行比较
D. 可以配合盲法
E. 两观察期间的洗脱期时间间隔不宜过短或过长

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1. This text is mainly about a father’s ________.

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C. lifestyle
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