单项选择题

Georges Valensi's patent lasted until 1971 because______.

A．nobody would offer and reward for his patent prior to that time
B．his patent could not be put to use for an unusually long time
C．the color TV receiver was not available until that time
D．there were not enough TV stations to provide color programmes
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单项选择题
The word plagiarize'(Line 6, Para 5) most probably means ______ .
A．steal and use
B．provide reward to
C．publicize
D．take and change
单项选择题
From the passage we get the impression that______.
A．an invention will not benefit the inventor unless it is reduced to commercial practice
B．patent experts often recommend patents to others by conducting a search through dead patents
C．an old patent is more expensive than a new one
D．products are actually inventions which were made a long time ago
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