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.

Example Input: Question: Since green plants make their own food, they are called (A) predators (B) prey (C) decomposers (D) producers?
Example Output: plants, make

Example Input: Question: Scientists can study the organisms that lived in a certain area over a million years ago by examining ___. (A) weather patterns (B) fossils (C) rings on trees (D) minerals?
Example Output: study, organisms, lived, area, million, years, ago, examining

Example Input: Question: A water company uses lab tests on the water supply before sending the water through pipes to people's homes. How do these lab tests help people? (A) by adding minerals and nutrients to the water (B) by checking the water to make sure it is safe to drink (C) by filtering chemicals and organisms out of the water (D) by stopping harmful substances from entering the water?
Example Output:
lab, tests, water, help, people?