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 soccer player kicks a soccer ball across a field. Which factor has the most effect on the distance the soccer ball travels? (A) the color of the ball (B) the force of the kick (C) the length of the field (D) the temperature of the air?

Ex Output:
soccer, ball, field., factor, effect, distance, ball, travels?


Ex Input:
Question: Which process results in an animal producing offspring? (A) digestion (B) respiration (C) reproduction (D) growth?

Ex Output:
process, animal, producing, offspring?


Ex Input:
Question: A student puts two identical plants in the same type and amount of soil. She gives them the same amount of water. She puts one of these plants near a sunny window and the other in a dark room. This experiment tests how the plants respond to (A) light (B) air (C) water (D) soil?

Ex Output:

identical, plants, soil., water., sunny, window, in, a, room., tests