题目内容：
下列何种情况下以人时为分母计算频率
参考答案：
答案解析：
单选题：下列何种情况下以人时为分母计算频率
- 题目分类：公卫助理医师
- 题目类型：单选题
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下列哪一项不是病例对照研究的特点
下列哪一项不是病例对照研究的特点
阅读短文，回答题。Donald Hall__________.
阅读短文，回答题。Donald Hall__________.
The word "blindsided" underlined in Paragraph 3 means
The word "blindsided" underlined in Paragraph 3 means
When people have no will to live, people are often very diff
When people have no will to live, people are often very difficult to help.
为了研究体重随身高的依存变化关系，宜选用
为了研究体重随身高的依存变化关系，宜选用