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: Surgery
A 27-year old male presents wio backache,that occurs early in the morgiii ited withstiffness, and persists for more than lutes. Onexamination. chest expansion is also icted. Thep,ol-)111-' ,,:,psis is: 
Select and explain. 
A. Rheumatoid ahritis, B. Oteoahritis, C. Gouty ahritis, D. Ankylosing spondylitis
D: Ankylosing spondylitis
Answer: D: Ankylosing spondylitis 
Explanation: Ans. d. Ankylosing spondylitis A 27-year old male presents with low backache that occurs early in the morning, associated with stiffness, and persists for more than 30 minutes. On examination, his chest expansion is also restricted. The most probable diagnosis is ankylosing spondylitis.