The term “atomic age” was first coined in the 1950s because of which of the following factors? (a) feelings of optimism toward nuclear energy in the years after world war ii. (b) fear in response to the threat of nuclear warfare that was prevalent throughout the cold war. (c) relief stemming from the belief that the atomic bombs in world war ii saved american lives. (d) anger in response to the use of the atomic bombs against japan at the end of world war ii.

(A) feelings of optimism toward nuclear energy in the years after World War II.

While there was "fear in response to the threat of nuclear warfare" in the 1950s (to use the terms of answer B), the popularity of the term "atomic age" had to do with optimism over harnessing nuclear power to change the world.  In 1949,  the chairman of the US Atomic Energy Commission chairman, had said that "atomic energy is not simply a search for new energy, but more significantly a beginning of human history in which faith in knowledge can vitalize man's whole life." That sort of feeling is what characterized the idea of "the atomic age."