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: On Earth, water can be a solid, a liquid, or a gas. Which energy source has the greatest influence on the state of matter of water? (A) the sun (B) the wind (C) ocean currents (D) the metal core?

Ex Output:
energy, source, greatest, influence, state, matter, water?

Ex Input:
Question: A squid is an animal that lives in the ocean. It pumps a stream of water out of its body, causing it to move rapidly. Which of the following mechanical systems moves in a way most similar to the squid? (A) a bus (B) a helicopter (C) a rocket (D) a train?

Ex Output:
squid, pumps, water, mechanical, systems, similar

Ex Input:
Question: Why does sunrise occur in New York City on the east coast a few hours before Los Angeles on the west coast of the United States? (A) The Earth's revolution around the Sun causes the east coast to be exposed to sunlight first. (B) The tilt of the Earth's axis tilts the east coast toward the Sun. (C) The east coast moves out of the Moon's shadow before the west coast. (D) The rotation of the Earth on its axis causes the east coast to be exposed to sunlight before the west coast.?

Ex Output:
sunrise, occur, east, coast, hours, west, coast