Answer:
O.D. Electronic computers.
Step-by-step explanation:
Electronic Numerical Integrator and Computer or ENIAC was the first electronic generated programmable computer that was invented in 1945 by John Mauchly, J. Presper Eckert, and designed by Eckert too. This electronic computer would be used for solving common problems like calculating numerical problems.
Made to solve "a large class of numerical problems", this electronic computer helped in calculating for the construction of hydrogen bombs. This calculating machine was also used during the Second World War. Parts of it are on display at Washington D.C.'s Smithsonian Institution.
Thus, the correct answer is option D.