单项选择题

It is implied in the passage ______.

A．measles is not usually a fatal disease
B．measles ceased to be problem by the seventeenth century
C．measles is the disease most commonly involved in virgin-soil epidemics
D．measles was not a significant problem in Spanish colonies

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单项选择题

The author's argument concerning the importance of epidemics in the decrease of Native Ameri cans would be weakened if ______.

A．there was a fixed evidence to determine the pre-Columbian population of the New world at only 80 million
B．spanish tribute recordsed showed periodic population fluctuations
C．documents gave sophisticated Native American medical procedures
D．fossils indicated Native American contact with smallpox prior to 1492

单项选择题

The primary purpose of the passage is to ______.

A．refute a common misconception
B．provide support for a hypothesis
C．suggest a solution to a dilemma
D．reconcile opposing viewpoints