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
Which of the following conditions can cause bony ankylosis? 
Select and explain. 
A. Rheumatoid ahritis, B. Pyogenic ahritis, C. Osteo ahritis, D. Traumatic ahritis
B: Pyogenic ahritis
Answer: B: Pyogenic ahritis 
Explanation: Pyogenic ahritis causes bony ankylosis.