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: A chemical property of a mineral is evident if the mineral (1) breaks easily when struck with a hammer (2) bubbles when acid is placed on it (3) is easily scratched by a fingernail (4) reflects light from its surface?
Example Output: chemical, property, mineral, evident

Example Input: Question: John looks at the moon one night and is only able to see a very small portion. In what phase is the moon? (A) (B) (C) (D)?
Example Output: moon, see, small, portion., phase

Example Input: Question: A student wants to organize a group of animals into two categories based on observable external features. Which display will most appropriately show the two categories of animals?
Example Output:
animals, two, categories, observable, external, features., display, categories