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: A student heated a pan of soup on a stove. While stirring the soup with a metal spoon, the student noticed the spoon became very warm. What is the most likely reason the spoon became warm? (A) The stirring action heated the spoon. (B) Warm air in the room heated the spoon. (C) Heat from the soup was transferred to the spoon. (D) The student's hand transferred heat to the spoon.?

Ex Output:
soup, metal, became, warm., reason


Ex Input:
Question: What motion causes day and night? (A) revolution of Earth (B) revolution of the Moon (C) rotation of Earth (D) rotation of the Moon?

Ex Output:
motion, causes, day, night?


Ex Input:
Question: Which adaptation allows a walrus to stay warm in cold water? (A) reddish coat (B) bristly mustache (C) wrinkled skin (D) thick layer of blubber?

Ex Output:

adaptation, walrus, stay, warm, cold, water?