This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Which of the following stages of gypsum expansion shows initial crystal growth? \nSelect and explain. \nA. I, B. II, C. III, D. IV', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Imagine that the initial mix is represented in the figure (stage I) by the three round particles of hemihydrate surrounded by water.\nUnder normal setting conditions, the crystals of the dihydrate begin to form on the nuclei. The water around the particles is reduced by hydration and these particles\xa0are\xa0drawn\xa0more\xa0closely\xa0together\xa0because\xa0surface tension of the water keeps the water surface area at a minimum (stage II).\nAs the crystals of dihydrate grow, they contact each other\xa0and\xa0the\xa0water\xa0around\xa0the\xa0particles\xa0again\xa0decreases (stage III).\nFurther\xa0dihydrate growth consumes more water and\xa0should\xa0draw\xa0the crystals\xa0together\xa0as\xa0before,\xa0but\xa0the outward thrust of the growing crystals opposes this contraction (stage IV).\nEventually, the crystals become intermeshed and entangled (stage V).\n\nKey Concept', 'role': 'assistant'}]