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: Which object is the best conductor of electricity?  (A) metal fork (B) rubber boot (C) plastic spoon (D) wooden bat.

SOLUTION: A.

PROBLEM: Question: Some *** *** *** before *** each year. This is an *** of  (A) migration (B) hibernation (C) germination (D) evaporation.

SOLUTION: E.

PROBLEM: Question: The Grand Canyon is a perfect example of ___, over millions of years, caused by the flow of the Colorado River.  (A) dissolving (B) deposition (C) weathering (D) erosio.

SOLUTION:
D.