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: Crows are found throughout many parts of the world. They are black birds with excellent hearing. In the wild they live for six to seven years. Some crows in Japan open hard-shelled nuts by dropping them in front of moving cars. Which of these is a learned behavior? (A) Having excellent hearing (B) Living six to seven years (C) Dropping nuts in front of cars (D) Having black feathers?

Ex Output:
Crows, hearing., live, open, nuts, learned, behavior?


Ex Input:
Question: Tim and Carla play catch with a ball. Which term describes the motion of a ball? (A) shape (B) size (C) speed (D) weight?

Ex Output:
ball., describes, motion, ball?


Ex Input:
Question: What color are chloroplasts? (A) green (B) red (C) blue (D) brown?

Ex Output:

color, chloroplasts?