单项选择题

The relative stability of the human population has been upset by ______.

A．the proportion of the reproductive age group
B．the influenza epidemic
C．advances in medical science
D．the Black Death in Europe
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单项选择题
The word vibrant probably means ______.
A．bright
B．light
C．soft
D．dark
单项选择题
What can we infer from the passage
A．Human's future could be depended on advance in medical science.
B．We could introduce certain kind of disease to control the number of some species.
C．Human could control diseases.
D．Introduction of the myxomatosis could control rabbit population in the world.
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