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
Water of reaction needed to react completely with
100 g of calcium sulphate hemihydrates to convert it to calcium sulphate dihydrate 
Select and explain. 
A. 18.6ml, B. 22.2ml, C. 30.4ml, D. 45.3ml
A: 18.6ml
Answer: A: 18.6ml 
Explanation: None