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: John was using his mp3 *** when it *** *** ***. What is the *** *** *** should do to *** *** the ***?  (A) recharge the battery (B) take the player apart (C) replace the player with a new one (D) change to a different son.

SOLUTION: E.

PROBLEM: Question: Which of the following represents a *** ***?  (A) a sugar cube dissolving in water. (B) ice cubes forming in a freezer. (C) ice cream melting in a bowl. (D) a cake baking in an oven.

SOLUTION: E.

PROBLEM: Question: Which *** help to *** *** such as *** that enter the human ***?  (A) red blood cells (B) liver cells (C) white blood cells (D) brain cell.

SOLUTION:
E.