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': 'Water of reaction needed to react completely with\n100 g of calcium sulphate hemihydrates to convert it to calcium sulphate dihydrate \nSelect and explain. \nA. 18.6ml, B. 22.2ml, C. 30.4ml, D. 45.3ml', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]