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According to the passage, Thomas Edison's first invention ....... .
When he was 21 years old, Thomas Edison took out his first patent. It was for an electric vote
counter to be used in the United States Congress. The machine worked perfectly, but the
congressmen would not buy it. They did not want vote counting to be done quickly, and the old
roll-call system was sometimes used for purposes of delay. This experience taught the young
inventor a lesson. He decided to follow a simple rule: "First be sure a thing is wanted or needed,
then go ahead." When he died at 84, Edison had patented 1,093 inventions, which included the
motion picture projector, electric light bulb, and hundreds of others. Many were among the most
useful and helpful inventions ever developed.