Detailed Instructions: In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").
Q: the earth's population could face severe depletion if which of these stopped happening? (A) the running man dance (B) the American Idol show (C) human gene cloning research (D) the food pyramid structure
A:
D