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
HLA B27 histocompatibility antigen is correlated with - 
Select and explain. 
A. Sjogren's disease, B. Ankylosing spondylitis, C. Felty's syndrome, D. Scleroderma
B: Ankylosing spondylitis
Answer: B: Ankylosing spondylitis 
Explanation: None