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: *** *** that *** is *** on its ***. He *** *** this *** is *** for the *** that a *** on *** *** ***. When the *** *** is *** *** the ***, what *** *** it be in ***?  (A) fall (B) spring (C) summer (D) winte.
[EX A]: E.

[EX Q]: Question: *** *** *** difference *** *** food chain *** *** food web?  (A) A food chain always ends with a primary consumer. (B) A food web is made up of many food chains. (C) A food web only shows one flow of energy through the ecosystem. (D) A food chain is made up of many food webs.
[EX A]: B.

[EX Q]: Question: *** *** *** change *** chemical *** *** iron?  (A) cause it to rust (B) cause it to melt (C) cut it into pieces (D) expose it to a magne.
[EX A]:
A.