单项选择题

Which of the following does NOT characterize a normal patent

A．some extension of life span
B．some duration of validity
C．some form of reward
D．some kind of monopoly
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单项选择题
An inventor can generally make a big profit if he _________ his or her invention.
A．publishes
B．keeps secret
C．patents
D．sells
单项选择题
The author of this passage is most probably _________ .
A．American
B．British
C．Chinese
D．Australian
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