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': 'True about x-ray diffraction data for set gypsum products: \nSelect and explain. \nA. There is less than 50% dihydrate present in type 4 stones, B. There is less than 40% dihydrate present in type 2 die materials, C. There is less than 30% dihydrate present in type 1 plaster, D. There is less than 20% dihydrate present in type 5 stones', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The setting reaction takes time to complete and changes in the mixture begin as soon as the hemihydrate and water\xa0are\xa0mixed\xa0together.\xa0 X-ray\xa0diffraction\xa0data\xa0for\xa0set\xa0gypsum products indicate that there is less than 50% dihydrate present\xa0in Type IV and V stones, about 60% in Type II die materials, and over 90% in Type I plasters.\nPhillips Science of Dental Materials ed 12 pg 184', 'role': 'assistant'}]