This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Posterior superior iliac spine is at the level of \nSelect and explain. \nA. L5, B. S1, C. S2, D. S3', 'role': 'user'}, {'content': 'Answer: C \nExplanation: PSIS line identifies the S2 spinous process most frequently', 'role': 'assistant'}]