本题目来源于试卷: Human Population Dynamics，类别为 IB环境系统与社会
[单选题]
Figure
population growth
With reference to the Figure, estimate the doubling time (DT) in years of the human population on Earth starting in 1960.
A. 123 years
B. 47 years
C. 39 years
D. 48 years
参考答案: C
本题详细解析:
Doubling time is the time taken for a po tuy7:+1 og)yrf c/p:bazo1mk pulation to double in size. In 1960 the human population was 3 billion. Looking for the year in which it was 6 billion, we find that was around 2000, although it was actually in 1999. fk+ :cy)7ozrb1:otau p/y 1gm
1999 - 1960 = 39 years to double from 3 to 6 billion
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