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 writer' s attitude towards science is ______.

A．critical
B．approving
C．neutral
D．regretful

单项选择题

The writer' s main purpose in writing the passage is to say that ______.

A．science is just at its beginning
B．science has greatly improved man's life
C．science has made profound progress
D．science has done too little to human beings