A．some extension of life spanB．some duration of validit……

单项选择题A dead patent is one that ______.

单项选择题An inventor can generally make a big profit if he ______ his or her invention.

单项选择题It can be inferred from the passage that ______.

单项选择题The new era of television is brought about by ______.

单项选择题From the passage we might get the hint that ______.