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 a mixture, a magnet is used to separate some particles from sand. The dark particles are most likely made of which element? (A) sodium (B) iron (C) sulfur (D) copper?
Example Output: magnet, separate, particles, sand., dark, particles, made, element?

Example Input: Question: Humans have bacteria inside as well as outside the body. These bacteria are __________. (A) both beneficial and harmful (B) harmful and spread disease (C) harmful all of the time (D) helpful all of the time?
Example Output: Humans, bacteria, inside, outside, body.

Example Input: Question: Ella has several wooden blocks. When Ella holds the blocks in her hand, she feels that they are rough. Which term best describes what Ella feels? (A) a prediction (B) a conclusion (C) a hypothesis (D) an observation?
Example Output:
wooden, blocks., blocks, rough.