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问题 选择题

人口自然增长率的大小取决于

A．经济发达程度

B．出生率和死亡率

C．生活医疗水平

D．文化教育水平

答案

答案：B

题目分析：

人口的自然增长主要是由人口的出生率和死亡率共同决定的，人口自然增长率=出生率-死亡率，故本题选B。

单项选择题

Dense snow cover can cause unusually harsh weather patterns to persist. If a severe winter storm blankets the Great Plains, the snow cover reflects the sun’s radiation back into space and thus keeps the temperature of the ground tow. Consequently, cold air moving down from Canada remains cold enough to cause more snowstorms.
Which of the following is a conclusion that can be properly drawn from the information above

A．Winter weather on the Great Plains is the product of unusual movements of air masses.

B．The Great Plains are more likely than other areas to suffer unusually harsh weather patterns.

C．If the Great Plains get more snow than usual early in the winter and the snow remains until the spring thaw, the winter is likely to be colder than usual.

D．Even if the temperatures on the Great Plains are not extremely cold but are just below freezing, a moderate snowstorm will probably turn into a blizzard.

E．(E) The temperature of the ground depends primarily on the thickness of the snow cover.
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单项选择题

临床上最常用的对龋病分类的方法是

A．按病变进展的速度分类
B．以上都不对
C．按病变所在的解剖部位分类
D．按病变深度分类
E．按病变的牙位分类
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