This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lower limb, Subject name: Anatomy
[{'content': 'Dermatome of posterior thigh : \nSelect and explain. \nA. L4, B. L5, C. S1, D. S2', 'role': 'user'}, {'content': "Answer: D \nExplanation: Dermatome for posterior calf and thigh is S2. Ref : Gray's Anatomy The Anatomical Basics of Clinical Practice 41 e pg 1324.", 'role': 'assistant'}]