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.

Example Input: Question: In the past, Native American Indians buried dead fish along with corn seeds. This technique was used because the decomposing dead fish would (1) provide nutrients for the growing corn plant (2) eliminate the need for weeding around the corn plant (3) release oxygen for use by the corn plant (4) supply all the water needed by the corn plant?
Example Output: Native, American, buried, dead, fish, corn, seeds., decomposing, fish

Example Input: Question: Which of the following systems breaks food into nutrients that can be used by the body? (A) circulatory. (B) digestive. (C) respiratory. (D) reproductive.?
Example Output: systems, breaks, food, nutrients, body?

Example Input: Question: In addition to oxygen, what do plants produce during photosynthesis? (A) chlorophyll (B) sugar (C) carbon dioxide (D) light energy?
Example Output:
plants, produce, photosynthesis?