This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology and Rheumatology, Subject name: Medicine
[{'content': 'Part of spine, involved in Rheumatoid arthritis is: \nSelect and explain. \nA. Cervical, B. Thoracic, C. Lumbar, D. Sacral', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' cervical spine (Ref. Harrison, 17/e p 2086 & 16/e, p 1971 (15/e, p 1932)).Rheumatoid arthritis commonly involves joints of hands, wrist, knees, elbow, ankle, feet in symmetrical* manner."The axial skeleton involvement is usually limited to upper cervical spine" - Harrison, 15/e, p. 1932.', 'role': 'assistant'}]