单项选择题

Scientists have discovered in the past few years that ______.

A．the exposure of DNA to the public is unnecessary
B．the tiny cell in DNA is a neat little machine
C．man actually knows nothing about DNA
D．man has much to learn about DNA

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单项选择题

What CAN'T be inferred from the 1st paragraph

A．Scientific experiments in the past three hundred years have produced many valuable items.
B．For three hundred years there have been people holding hostile attitude toward science.
C．For centuries scientific discoveries have been hailed by the human world unanimously.
D．Three hundred years is not long enough to settle back for critical appraisal of the scientific method.

单项选择题

Man's attitude toward scientific discoveries has always been ______.

A．suspicious
B．undoubting
C．cynical
D．critical