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': 'Dendrites in cast alloys form by mechanism of \nSelect and explain. \nA. constitutional superconductivity, B. constitutional supercooling, C. constitutional supergriting, D. constitutional supergraining', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]