This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Rheumatoid Arthritis, Subject name: Medicine
Rheumatoid arthritis commonly affects the - 
Select and explain. 
A. Cervical spine, B. Thoracolumbar spine, C. Lumbar spine, D. Sacral spine
A: Cervical spine
Answer: A: Cervical spine 
Explanation: Ans. is 'a' i.e., Cervical spine o In decreasing frequency, the metacarpophalangeal (MCP), wrist, proximal interphalangeal (PIP), knee, metatarsophalangeal (MTP), shoulder, ankle, cervical spine, hip, elbow and temporomandibular joints are most commonly affected.