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: Which of the following statements best explains why magnets usually stick to a refrigerator door? (A) The refrigerator door is smooth. (B) The refrigerator door contains iron. (C) The refrigerator door is a good conductor. (D) The refrigerator door has electric wires in it.?

Ex Output:
magnets, stick, refrigerator


Ex Input:
Question: Which tool would a student use to measure wind speed? (A) compass (B) barometer (C) anemometer (D) weather vane?

Ex Output:
tool, measure, wind, speed?


Ex Input:
Question: Nectar feeding bats provide pollination to many tropical rain forest plants. If the nectar feeding bats became extinct, then these plants would most likely__________. (A) increase in population and create more energy (B) decrease in population and disrupt the food chain (C) have no effect on the population of the plants (D) pollinate themselves?

Ex Output:

bats, pollination, rain, forest, plants., plants