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问题 单项选择题

最近国务院关于我国人口发展报告指出，2050年我国进入老龄化社会，人口出现负增长。这一预测的主要依据是（）

A.人口数量

B.人口密度

C.性别比例

D.年龄组成

答案

参考答案：D

解析：试题分析：年龄组成可以预测种群密度的变化趋势，由题意可以看出，我国人口发展报告指出了我国人口的变化趋势，故D正确。

填空题

假如你是Judy，请你根据你的成绩单，给你妈妈写一封信，汇报你的成绩。

Dear Mom,

      How's it going? Things are fine here. I got my report card today. Luckily, I did OK this time.

My English teacher said I was    1      My math teacher said l was    2    and my P.E. teacher said 

I was     3    in class. However, my history teacher said I    4   . Another disappointing result was

in science. My science teacher said l was a    5    student.   

     Well, that's all about the news I have for now. I will have to try harder at science.

                                                                                                                                Love,

                                                                                                                                   Judy

1._____2._____3._____4._____5.______
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单项选择题

经空气传播的疾病的流行特征是（）。

A.疾病的发生与季节有关，多见于冬春季

B.传播广泛，发病率高

C.在未经免疫的人群中，发病率呈周期性变化

D.儿童多发

E.以上都是
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