流行病学研究的主要用途是( )A．进行统计学检验 B．探讨病因_爱下问搜题

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问题单项选择题

流行病学研究的主要用途是( )

A．进行统计学检验

B．探讨病因与影响流行的因素及确定预防方法

C．研究疾病的发生概率

D．研究疾病的临床表现

E．研究疾病的死亡情况

答案

参考答案：B

解析：流行病学研究的主要用途有以下几方面：病因学研究、疾病预防与控制、疾病监测、对疾病防治、卫生服务活动进行研究和评价、研究疾病的自然史等。

阅读理解

阅读理解。

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1. Mrs. Lin wants to ask a babysitter to look after her ______.

A. grandfather
B. grandmother
C. daughter
D. son

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A. 4
B. 5
C. 6
D. 7

3. The babysitter will usually work ______.

A. in the afternoon
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4. Mrs. Lin will pay ______ for the babysitter's work from Monday to Friday.

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单项选择题

维持细胞外液渗透压的重要离子是（）

A.K⁺

B.Na⁺

C.Mg²⁺

D.H⁺

E.Ca²⁺