The most probable answer would be (C) AC Electric Power.
All of the options that are presented in the problem are all associated with Thomas Edison except for the AC Electric Power. In the times of the War of the Currents between him and Nikola Tesla, the inventor of the AC Electric Power. The Phonograph, the Incandescent light bulb, the motion picture camera, and the universal stock ticker were all associated with Thomas Edison. The Phonograph was invented by him at around 1877. The incandescent light bulb was at around 1879. The motion picture camera, on the other hand, was at around 1889, while universal stock ticker was at around 1869.
