A—overpopulation B—under population
C—working population D—population waiting for employment
E— population F—rural population
G—population reproduction H—population increase
I—population decrease J—population base
K—population distribution L—population density
M—population quality N—population pyramid
O—population statistics P—population theory
Q—population studies
51. ( )在业人口 ( )人口密度
52. ( )人口增长 ( )人口年龄金字塔
53. ( )城市人口 ( )人口质量
54. ( )人口理论 ( )人口分布
55. ( )待业人口 ( )人口过剩