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 *** *** an *** by *** *** *** *** *** of *** for a ***. At the *** of the ***, she *** the *** mice. *** the *** is an *** of  (A) a measurement (B) a hypothesis (C) an explanation (D) background researc.
[EX A]: E.

[EX Q]: Question: A student found a *** while hiking in the mountains. By *** at the rock, she could *** the  (A) exact weight of the rock. (B) length of time the rock had been on the hiking path. (C) color and shape of the rock. (D) exact length of the rock.
[EX A]: C.

[EX Q]: Question: *** *** *** is *** of a *** *** that slowly *** on *** where __________.  (A) continental plates collided (B) oceanic plates pulled apart (C) a continental and an oceanic plate pulled apart (D) a continental and an oceanic plate collide.
[EX A]:
E.