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: Which of the following uses electric motors to work? (A) Roller skates and baby strollers (B) Lawn mowers and cars (C) Stopwatches and clocks (D) Skateboards and bicycles?
Example Output: uses, electric, motors

Example Input: Question: Rachel purchased a kit for making a skateboard ramp. Which of the following is most important to have for putting the ramp together? (A) a picture showing the colors of different ramp parts (B) a diagram showing some ways to use the ramp (C) a list of prices for other available kits (D) a set of instructions for the kit materials?
Example Output: skateboard, important, putting, together?

Example Input: Question: Scientists observed several different organisms in the same forest environment. Which of the following organisms in this forest environment depend on dead plant and animal material for food? (A) cockroach (B) tree (C) snake (D) robin?
Example Output:
depend, dead, plant, animal, material, food?