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'.

[EX Q]: Question: A student wants to look under a heavy rock. Which simple machine would be BEST to use to lift the rock?  (A) Wheel and axle (B) Lever (C) Inclined plane (D) Scre.
[EX A]: B.

[EX Q]: Question: Which structure does a plant cell have that an animal cell does not have?  (A) Vacuole (B) Cytoplasm (C) Cell membrane (D) Cell wal.
[EX A]: A.

[EX Q]: Question: Time ***, such as seconds, minutes, hours, weeks, and months are based on the  (A) records from history. (B) natural motions of the sun. (C) natural motions of the Earth. (D) natural motion of the moon.
[EX A]:
C.