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: Anatomy
[{'content': 'Os trigonum is which type of epiphysis ? \nSelect and explain. \nA. Aberrant, B. Pressure, C. Atavistic, D. Traction', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Atavistic', 'role': 'assistant'}]