The correct option is D.
The metaphor is a figure of speech which describes someone or something in a way that is not literally true. It is used to compare two things in an implicit way.
The global threat of nuclear warfare metaphor is represented by "the dark powers of destruction unleashed by science engulf all humanity in planned or accidental self-destruction."
The phrase "the dark powers of destruction unleashed by science" clearly stands for nuclear weapons, which were created by scientists. The case of "planned or accidental self-destruction." also refers to nuclear power events many of which occurred in the history of the world either by accident or were programmed.