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 Q]: Question: A see-saw is an example of which type of simple machine? (A) lever (B) pulley (C) wheel (D) inclined plane?
[EX A]: see-saw, machine?

[EX Q]: Question: Rachel purchased a kit for making a skateboard ramp. Which of the following is most important to have for putting the ramp together? (A) a picture showing the colors of different ramp parts (B) a diagram showing some ways to use the ramp (C) a list of prices for other available kits (D) a set of instructions for the kit materials?
[EX A]: skateboard, important, putting, together?

[EX Q]: Question: Which human activity is most harmful to the natural environment? (A) swimming in a lake(B) riding a bicycle(C) cutting down a rain forest(D) using solar energy?
[EX A]:
activity, harmful, environment?