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'.

Example Input: Question: The Grand *** is a *** example of ___, over millions of years, *** by the *** of the Colorado River.  (A) dissolving (B) deposition (C) weathering (D) erosio.
Example Output: D.

Example Input: Question: The *** heard when a *** *** is *** is caused by  (A) vibration. (B) refraction. (C) momentum. (D) acceleration.
Example Output: A.

Example Input: Question: Scientists *** several *** *** in the same *** environment. Which of the following *** in this *** *** *** on *** *** and *** *** for ***?  (A) cockroach (B) tree (C) snake (D) robi.
Example Output:
E.