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

Special words used in technical discussion______.

A．never last long
B．should be confined to scientific fields
C．may become part of common speech
D．are considered artificial language speech

单项选择题

The writer of the article was, undoubtedly______.

A．a linguist
B．an attorney
C．a scientist
D．an essayist