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 number of the bellbird in New Zealand got controlled by ______.
A．the decrease in distribution
B．human predation
C．deliberate introduction of its enemy animal
D．spread of certain kind of disease
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单项选择题
The word scrutiny ( Par
A．3 ) most probably means ______.A. inquiryB. observationC. control.D. suspicion
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