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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单项选择题

Which of the following is TRUE according to the passage

A．When a patent becomes out of effect, it can be re-patented or extended if necessary.
B．One can get all the details of a patented invention from a library attached to the patent office.
C．A patent holder must publicize the details of his invention when its legal period is over.
D．An inventor needs to apply for a patent before he makes his invention public.

单项选择题

According to the passage, which of the following is not true about Ariel

A．It is the best seller in Czechoslovakia.
B．It is a laundry detergent product.
C．Ariel was born outside the United States.
D．It already becomes popular in Europe.