You are given an elementary science question along with a few answer options. List all the words from the question that are essential and sufficient for choosing the correct answer option. Keep in mind that essential words are necessary to understand the meaning of the given question. However, non-essential words provide little information needed to select the correct answer. You can think about it like this: If the question was in another language, knowing the meaning of which words were necessary and enough for you to understand the question and answer it?. If your answer consists of multiple spans of words from the question, separate those using a comma (", "). Do not generate any word that is not present in the question. Make sure that your response is contained in the given question and the words are in the same order as the question.
 Grammatical correctness is not important.

[EX Q]: Question: When we eat pizza, it is digested by the body to provide us energy. This is an example of extracting which kind of energy? (A) chemical (B) light (C) heat (D) kinetic?
[EX A]: eat, digested, energy., example, extracting, energy?

[EX Q]: Question: The length of time from an animal's birth until its death is called its (A) life span. (B) instinct. (C) life cycle. (D) development.?
[EX A]: length, time, animal's, birth, death

[EX Q]: Question: A student pours a clear liquid from a test tube into a beaker with a clear liquid already in it and notices that the mixture turns pink. The student infers the two clear liquids are different. This inference is a result of (A) class discussion. (B) previous knowledge. (C) temperature changes. (D) student observations.?
[EX A]:
liquid, mixture, turns, pink., infers, liquids, different., inference, result