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: What causes nighttime and daytime on Earth? (A) the Sun rotating on its axis (B) Earth rotating on its axis (C) Earth revolving around the Sun (D) the Moon revolving around Earth?
Example Output: causes, nighttime, daytime, Earth?

Example Input: Question: In Florida, both panthers and bobcats prey on white-tailed deer. How will their competition for food most likely be affected if white-tailed deer populations in Florida suddenly decreases? (A) Competition will increase between bobcats and panthers. (B) Competition will decrease between bobcats and panthers. (C) Competition will increase between white-tailed deer and bobcats. (D) Competition will decrease between white-tailed deer and panthers.?
Example Output: panthers, bobcats, prey, deer., competition, food, affected, deer, populations, decreases?

Example Input: Question: Darwin's theory that animal species can change over time was inspired by his research on which set of islands? (A) the Philippine Islands (B) the Virgin Islands (C) the Hawaiian Islands (D) the Galapagos Islands?
Example Output:
Darwin's, theory, species, time, inspired, research, islands?