单项选择题

What social scientists have long felt puzzled about

A．The mortality rate can not be predicted.
B．The death toll remained stable year after year.
C．A quota for each type of death has not come into being.
D．People lost their lives every year for this or that reason.

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热门试题

单项选择题

In his research, Gerald Wilde finds that technological advances and increases in safety standards have ______.

A．helped solve the problem of so high death rate
B．oddly accounted for mortality rates in the past century
C．reduced mortality rates for violent and accidental deaths
D．achieved no effect in bringing down the number of deaths

单项选择题

Which of the following may contribute to a longer life span

A．Showing adequate trust instead of suspicion of others.
B．Eating the food low in fat and driving with great care.
C．Cultivating an optimistic personality and never losing heart.
D．Looking on the bright side and developing a balanced level of risk.