城市人口的自然增长率是指( )。
A．一定年限内，平均每年人口增长的速度
B．一年内城市人口自然增长的速度
C．出生人数与死亡人数的净差值
D．都不对
参考答案：B
解析：[试题解析] 自然增长是指出生人数与死亡人数的净差值。通常以一年内城市人口的自然增加数与该城市总人口数(或期中人数)之比的千分率来表示其增长速度，称为自然增长率。机械增长是指由于人口迁移所形成的变化量。机械增长的速度用机械增长率来表示，即一年内城市的机械增长的人口数对年平均人数(或期中人数)之千分率。人口平均增长速度(或人口平均增长率)指一定年限内，平均每年人口增长的速度。城市的人口主要受到自栈增长和机械增长的影响， 两者之和便是城市人口的增长值。
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| As she walked round the large shop, Edith realized how difficult it was to choose a suitable Christmas 1 for her father. She 2 that he were as easy to please as her mother, who was 3 satisfied with perfume (香水). 4 , shopping at this time of the year was a most 5 job. People 6 on your feet, pushed you with their shoulders and almost 7 you over in their hurry in order to 8 something cheap ahead of you. Partly to have a rest, Edith paused in front of a counter, where some beautiful ties were on 9 . "They are 10 silk," the shop assistant told her with a smile trying to 11 her to buy one. But Edith knew from past 12 that her choice of ties hardly ever pleased her father. She moved on slowly and then, quite by chance, 13 where a small crowd of men had gathered round a counter. She found some fine pipes (烟斗) on sale and the 14 were very beautiful. Edith did not hesitate for long, although her father 15 smoked a pipe once in a while, she believed this was 16 to please him. When she got home, with her small but 17 present hidden in her handbag, it was time for supper and her parents were already 18 table. Her mother was in great 19 . "Your father has at last decided to stop smoking," she told her daughter happily. Edith was so 20 that she could not say a single word. | ||||
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