instruction:
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'.
question:
Question: The *** heard when a *** *** is *** is caused by  (A) vibration. (B) refraction. (C) momentum. (D) acceleration.
answer:
A.


question:
Question: The movement of soil by wind or water is called  (A) condensation (B) evaporation (C) erosion (D) friction.
answer:
C.


question:
Question: What is an *** of ***?  (A) It is a natural way to separate the strong from the weak. (B) It always results in adaptations. (C) It decreases the size of strong populations. (D) Competition is selfish and has no advantages.
answer:

E.