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: One example of a consumer is ___. (A) a tree (B) bacteria (C) a reindeer (D) a rose?
Example Output: example, consumer

Example Input: Question: ____ is (are) composed of broken down pieces of living and nonliving Earth materials. (A) plants (B) soil (C) animals (D) the sun?
Example Output: composed, pieces, living, nonliving, materials.

Example Input: Question: A student is investigating changes in the states of matter. The student fills a graduated cylinder with 50 milliliters of packed snow. The graduated cylinder has a mass of 50 grams when empty and 95 grams when filled with the snow. During which process in the water cycle does snow fall to the ground? (A) classification (B) condensation (C) evaporation (D) precipitation?
Example Output:
process, water, cycle, snow, fall