Given the task definition, example input & output, solve the new input case.
You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
Example: Which part of a bicycle BEST moves in a circle?
(A) Seat (B) Frame (C) Foot pedal (D) Kickstand
Output: C
Seat, frame and Kickstand are static parts of the bicycle, even when bicycle moves. Foot pedal moves in a circle as bicycle moves.

New input case for you: The crews of two boats at sea can communicate with each other by shouting. Why is it impossible for the crews of two spaceships a similar distance apart in space to do this?
(A) The sound is reflected more in space. (B) The pressure is too high inside the spaceships. (C) The spaceships are traveling faster than sound. (D) There is no air in space for the sound to travel through.
Output:
D