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 Input:
Question: What should a student do when a glass beaker shatters during a laboratory experiment? (A) Notify the teacher. (B) Sweep the pieces into a pile. (C) Pick up the pieces and throw them away. (D) Leave it until the experiment is complete.?

Ex Output:
student, glass, beaker, shatters, experiment?


Ex Input:
Question: Which area is coldest? (A) rainforest (B) tundra (C) grassland (D) reef?

Ex Output:
area, coldest?


Ex Input:
Question: Alex looked at an electric toothbrush that had a plug with three metal prongs. Why are these prongs made out of metal? (A) Metal doesn't get hot and melt when you plug it into the outlet. (B) Metal is strong and is less likely to break when you plug it into the outlet. (C) Metal is an insulator and prevents shocks when you plug it into the outlet. (D) Metal is a conductor and completes a circuit when you plug it into the outlet.?

Ex Output:

electric, plug, metal, prongs., prongs, made, metal?