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.

Input: Consider Input: Question: Since green plants make their own food, they are called (A) predators (B) prey (C) decomposers (D) producers?

Output: plants, make


Input: Consider Input: Question: An antelope is running away from a lion. Which two body systems are working together to allow the antelope to run away? (A) Muscular and digestive (B) Muscular and skeletal (C) Circulatory and skeletal (D) Nervous and excretory?

Output: body, systems, together, allow, antelope, run


Input: Consider Input: Question: What muscle pumps blood throughout the body? (A) Skeletal muscle (B) Stomach muscle (C) Heart muscle (D) Lung muscle?


Output: muscle, pumps, blood