单项选择题

Which of the following statements is true

A．Diseases caused by bacteria and viruses were incurable in 1900.
B．Bacteria and viruses are the main causes of death today.
C．Medicines for curing pneumonia were not available in 1900.
D．Pneumonia caused as many deaths in 1900 as cancer does today.

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热门试题

单项选择题

On an average, people in America who were born in 1900 ______.

A．had a life-span of 74 years
B．lived a shorter but better life than those born later
C．lived to 47 years of age
D．lived 27 years longer than those born in 1981

单项选择题

In the first paragraph, the author gives the definitions of some terms in order to ______.

A．argue for the similarities between animal societies and human societies
B．smooth out the conflicts in human societies
C．distinguish between two kinds of opposition
D．summarize the characteristic features of opposition and cooperation