单选题 The conclusion which can be drawn safely from the second paragraph is that ______.

A、 a population growth from natural increase leads to a greater proportion of the work force
B、 a large population does not necessarily mean a higher proportion of work force
C、 the larger the number of the aged in a population, the higher the proportion of the work force
D、 if the population has an evenly spread age distribution, the work force will be lower

【正确答案】 B

【答案解析】解析：第二段主要是论述age distribution对劳动力规模的影响。