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.It is necessary for an inventor to apply for a patent before he makes his invention public. C.A patent holder must publicize the details of his invention when its legal period is over. D.One can get all the details of a patented invention from a library attached to the patent office.

时间:2023-10-05 07:59:51

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