Impromptu is an unrehearsed speech. Not rehearsing would not allow speakers to gather 100% of their thoughts.
The correct answer is B, i think sorry if im wrong.
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Explanation:
Thomas Edison created many inventions, but his favorite was the phonograph. While working on improvements to the telegraph and the telephone, Edison figured out a way to record sound on tinfoil-coated cylinders. In 1877, he created a machine with two needles: one for recording and one for playback.