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").

Example input: Deserts are in extremely dry environments, so liquids will naturally be (A) rainbow (B) plentiful (C) meager (D) talented
Example output: C
Example explanation: This is a good example and the output correctly answers the question.
Q: Winter solstice occurs on a day when (A) the sun is brightest (B) the sun is eclipsed (C) the moon is full (D) the darkness is greatest
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
D