TASK DEFINITION: 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'.
PROBLEM: Question: The *** heard when a *** *** is *** is caused by  (A) vibration. (B) refraction. (C) momentum. (D) acceleration.

SOLUTION: A.

PROBLEM: Question: *** and *** are necessary for ____ to ***.  (A) plants (B) animals (C) both plants and animals (D) nonliving thing.

SOLUTION: E.

PROBLEM: Question: When an *** feels threatened, it can release black *** into the water. The *** MOST likely helps the ***  (A) move quickly through the water. (B) breathe oxygen from the water. (C) hide from predators. (D) use food faster.

SOLUTION:
C.