In this task, you need to answer basic science questions. For each question, several terms are intentionally masked with ***. This masking can cover very few or many of the question words. Clearly, if masked terms are important, the modified question will be impossible to answer. Please indicate the correct answer with one of the following responses: "A", "B", "C", "D" or "E". While "A"-"D" correspond to the answer options provided in the input, "E" represents "I don't know" for questions that do not provide enough information. Respond via "E" if the question is not answerable. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'.

[EX Q]: Question: Which physical *** do some *** have that helps them *** in the Arctic?  (A) growing tall to hide in trees (B) changing fur color to hide from predators (C) developing large paws to protect themselves from the wind (D) producing shallow root systems to protect themselves from the cold ai.
[EX A]: E.

[EX Q]: Question: Roger Bacon is credited for developing the *** ***. His *** of which of these was most useful for this development?  (A) Light (B) Sound (C) Gravity (D) Electricit.
[EX A]: E.

[EX Q]: Question: A student found a *** while hiking in the mountains. By looking at the rock, she could tell the  (A) exact weight of the rock. (B) length of time the rock had been on the hiking path. (C) color and shape of the rock. (D) exact length of the rock.
[EX A]:
C.