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.

[Q]: Question: Which is the best example of a pure substance?
[A]: example, pure, substance?


[Q]: Question: The snowshoe hare sheds its fur twice a year. In the summer, the fur of the hare is brown. In the winter, the fur is white. Which of these statements best explains the advantage of shedding fur? (A) Shedding fur keeps the hare clean. (B) Shedding fur helps the hare move quickly. (C) Shedding fur keeps the hare's home warm. (D) Shedding fur helps the hare blend into its habitat.?
[A]: snowshoe, hare, explains, advantage, shedding, fur?


[Q]: Question: During a lab investigation, students were asked to determine the best way to clean up an oil spill using different materials.?
[A]:
materials, recorded, observations, material, absorbed, oil., ask, repeat, tests?