In this subtask, you will answer a simple science question. Please indicate the correct answer. If you're not sure about the answer, choose the last option "I don't know". Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'. The "A"-"D" responses correspond to the answer options mentioned in the input. There is a 5th option "E" which should be used for questions for which you're not sure about the answer (e.g., when the questions do not provide enough information to answer).

Let me give you an example: Question: When a guitar string is plucked, sound is produced by  (A) the size of the guitar. (B) the metal on the guitar. (C) the wood on the guitar. (D) the vibrations of the string.
The answer to this example can be: D.
Here is why: We know that the vibrations of the string produces sound in a guitar. So, the correct answer has to be "D".

OK. solve this:
Question: What characteristic helps a rabbit survive in a winter environment?  (A) size (B) strength (C) long ears (D) camouflag?
Answer:

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.