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.

[Q]: Question: In what way can bacteria be good for the human body? (A) Bacteria help the body have strong bones. (B) Bacteria help maintain body temperature. (C) Bacteria help deliver oxygen to the cells. (D) Bacteria help break down food.?
[A]: bacteria, good, human, body?


[Q]: Question: David was walking through his neighborhood and found a rock that had imprints of shells. What can you conclude about that area? (A) The area was once covered with trees. (B) The rock was carried there by the wind. (C) There had once been an ocean or river located there. (D) The area had a large amount of snow at one time.?
[A]: rock, imprints, shells., conclude, area?


[Q]: Question: A student is investigating changes in the states of matter. The student fills a graduated cylinder with 50 milliliters of packed snow. The graduated cylinder has a mass of 50 grams when empty and 95 grams when filled with the snow. The packed snow changes to liquid water when the snow is put in a warm room. Which statement best describes this process? (A) Cooling causes the snow to melt. (B) Cooling causes the snow to freeze. (C) Heating causes the snow to freeze. (D) Heating causes the snow to melt.?
[A]:
changes, matter., snow., snow, changes, liquid, water, warm, room., process?