This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
[{'content': 'Which of the following is the least common site of pain in a case of rheumatoid ahritis? NOT RELATED- OHO \nSelect and explain. \nA. Cervical, B. Knee, C. Low back, D. Ankle', 'role': 'user'}, {'content': 'Answer: C \nExplanation: .', 'role': 'assistant'}]