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: Ten people became sick with the flu after attending a school dance. What is the scenario that could best explain how the people got sick?
[EX A]: sick, flu, dance., explain, got, sick?

[EX Q]: Question: Two pool (billiard) balls collide, causing each to move in a different direction. Eventually, both come to a stop. The most important factor in causing them to stop is?
[EX A]: balls, move, different, direction., stop., factor, causing, stop

[EX Q]: Question: Which of the following would result in a decrease in the polar bear population in the arctic? (A) An increase in the amount of grass (B) An increase in the fish population (C) A decrease in the fish population (D) A decrease in the human population?
[EX A]:
decrease, polar, bear, population, arctic?