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.

Question: Skyler is selecting the kind of paper he wants to use to make a greeting card. He wants to select paper that does not tear easily. Which of the following features of the paper is most important for Skyler to consider? (A) color (B) size (C) smoothness (D) thickness?
paper, tear, easily., features, important

Question: Students are learning about the natural resources in Maryland. One group of students researches information about renewable natural resources in the state. The other group researches information about nonrenewable natural resources in the state. The resources the students investigate include plants, animals, soil, minerals, water, coal, and oil. Which nonrenewable natural resource heats homes? (A) sunlight (B) aluminum (C) natural gas (D) ocean waves?
nonrenewable, natural, resource, heats, homes?

Question: Which situation has had the most negative effect on the ecosystems of Earth? (A) Use of air pollution controls (B) Use of natural predators to control insect pests (C) Recycling glass, plastic, and metals (D) Increasing human population?

negative, effect, ecosystems