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 student is investigating a light bulb that saves energy and can last up to 10 times longer than other bulbs. Other than saving energy, which is another benefit of using these light bulbs? (A) Drinking water stays clean. (B) Less trash is put in landfills. (C) More nutrients are added to the soil. (D) Fewer chemicals get into the food supply.?
Example Output: light, bulb, benefit, light, bulbs?

Example Input: Question: Which unit of measurement describes an object's length? (A) meter (B) kilogram (C) liter (D) degree?
Example Output: unit, measurement, length?

Example Input: Question: A dog gets the energy it needs to run from (A) the air (B) the Sun (C) food (D) water?
Example Output:
dog, gets, energy