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: Medicine
Part of spine, involved in Rheumatoid arthritis is - 
Select and explain. 
A. Cervical, B. Thoracic, C. Lumbar, D. Sacral
A: Cervical
Answer: A: Cervical 
Explanation: None