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': 'A cast is poured with polysulphide impression material, but details are not achieved in cast. For achieving that what should be done? \nSelect and explain. \nA. Adding surfactant to gypsum, B. Mixing surfactant to impression material, C. Spraying water to gypsum, D. Spraying water + mixing surfactant to gypsum', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Absence of ﬁne details in cast poured with polysulﬁde impression materials indicates its hydrophobic property.\nA nonionic surfactant can be added to the impression materials in the manufacturing process to produce a degree of hydrophilicity to the surface of the material.\nThe beneﬁcial eﬀect of optimal surfactant mixing at the time of manufacturing is not reduced by rinsing the impression prior to pouring, so ﬁne details can be achieved on cast too.', 'role': 'assistant'}]