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.

Ex Input:
Question: A student boils 100 grams of water to form water vapor (gas). What method should the student use to determine that the mass of the water vapor is equal to 100 grams? (A) measuring the amount of water vapor (gas) in the air (B) collecting the water vapor (gas) and cooling it back to a liquid (C) weighing the beaker before and after the water is boiled (D) comparing the temperature of the boiling water to the temperature of the water vapor (gas)?

Ex Output:
method, determine, mass, water, vapor


Ex Input:
Question: The most important safety rule is (A) follow all instructions. (B) heat all substances before smelling. (C) clean all equipment. (D) mix all chemicals before starting an experiment.?

Ex Output:
important, safety, rule


Ex Input:
Question: When animals move to a warmer climate to avoid the change in seasons, we call this (A) hibernation. (B) camouflage. (C) perspiration. (D) migration.?

Ex Output:

animals, move, warmer, climate, avoid