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'.

[Q]: Question: *** is learning about *** ***s of ***. Which is an *** of a *** ***?  (A) webbed feet on a duck (B) migration of songbirds (C) sharp eyesight of an eagle (D) camouflaged colors on a fro.
[A]: E.


[Q]: Question: Which of the following *** can be *** into several ***?  (A) nitrogen (B) zinc (C) air (D) aluminu.
[A]: E.


[Q]: Question: A *** on top of a mountain is measured at 30 *** high in 1957. Fifty years later, in 2007, the *** is measured again and is now 21 *** high. What term best describes the *** for the rock's *** in ***?  (A) weathering (B) wind erosion (C) water erosion (D) chemical erosio.
[A]:
E.