instruction:
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:
Question: During an experiment, a student reports that a liquid turned green when mixed with another liquid. This is an example of (A) a measurement (B) a prediction (C) an explanation (D) an observation?
answer:
liquid, turned, green, mixed, liquid.


question:
Question: A student divides several cubes into two groups, based on whether or not each cube can float in later. What property is the student using to classify the cubes?
answer:
divides, cubes, two, cube, float, property, classify, cubes?


question:
Question: Scientists group animals based on physical features. Trout are classified as fish because of what physical feature? (A) Fish have gills. (B) Fish eat the same food. (C) Fish live in the same area. (D) Fish have the same predators.?
answer:

Trout, classified, fish, physical, feature?