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]
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In 1999, the human population was 6 billion.
In 2011, the milestone of 7 billion was reached.
In 2022, 8 billion people inhabited Earth.
In 2014, the UN predicted that we would reach between 9.6 and 12.3 billion people by 2100 and continue growing somewhat after that.
In 2022, the UN predicted a maximum of 10.4 billion people in the 2080s.
Suggest which reason does not explain the differences between the UN projections.
A. A slower increase in life expectancy has been observed, with a maximum. This is instead of a steady increase in life expectancy without an upper limit.
B. The model used gives more accurate predictions when the time to the maximum is shorter.
C. A more rapid decrease in fertility in some countries in Africa has been observed than was expected.
D. The model used by the UN helps us understand population growth but cannot help predict the future.
参考答案: D
本题详细解析:
Models can both help us understand populatioqq3u mb*z6hkw:h sx/6 n growth as well as predict what may happen in the future. Option D is, therefore, the correct answer.
Predictions made by models become more uncertain the farther into the future you look as the number of uncertainties inchs b66zx:q uq3wm/k*hreases. Option B is, therefore, a true statement and not the correct answer.
Life expectancy has been increasing steadily. In 2014 it was not clear that there was a maximum or what age this would be; life expectancy was predicted to increase beyond 100 years old. By 2022 it was clear that advancements in medicine would not remove limits on life expectancy, and it was observed that life expectancy is increasing more slowly as it gets closer to this limit. Option A is a true statement and not the correct answer.
The total fertility rate (TFR) is currently the main cause of human population growth. In 2014 it was only slowly decreasing in many parts of Africa. By 2022 it was clear that the TFR was decreasing more rapidly than expected, leading to much lower population growth. Option C is thus true and not the correct answer.
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