The correct answer is D. Electrical power.
Step-by-step explanation
Nikola Tesla (1856 - 1943) was a Serbian engineer who developed advances that influenced the industrial revolution, these were related to electromagnetism, considered as the basis for growth in the field of alternating current in electrical energy.
Thomas Alva Edison (1847 - 1931) was an American inventor who stood out for his research and the production of objects related to electricity such as the battery for cars, the phonograph, the light bulb, besides developing a system of generation and distribution of energy for houses.
George Westinghouse (1846 - 1914) was a contemporary American inventor to Thomas Alva Edison, with whom he had a rivalry because Westinghouse was a supporter of alternating current electric power, while Alva Edison was a supporter of direct current. Also, he stood out for the creation of the railway pneumatic brake.
According to the above, the three characters were great inventors in the field of electrical power through electrical energy. So, the correct answer is D. Electrical power