单项选择题

Now scientists have found in the past few years______.

A．the exposure of DNA to the public is unnecessary
B．the tiny cell in DNA is a neat little machine
C．man knows nothing about DNA
D．man has much to learn about DNA
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单项选择题
The principle discovery in this century shows______.
A．man has overthrown Newton' s laws of physics
B．man has solved a new set of gigantic puzzles
C．man has lost many scientific discoveries
D．man has given up some of the once accepted theories
单项选择题
What can' t be inferred from the 1 st 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．Modern civilization depends on science so man supports scientific progress unanimously.
D．Three hundred years is not long enough to settle back critical appraisal of scientific method.
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