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
Commonest degenerative joint disease in- 
Select and explain. 
A. Gout, B. Osteoporosis, C. Rheumatoid arthritis, D. Osteo arthritis
D: Osteo arthritis
Answer: D: Osteo arthritis 
Explanation: None