This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Prostate Cancer, Subject name: Surgery
A 65 year old male was diagnosed with prostate cancer three years back and was treated by surgery and hormone therapy. Presently he has developed urinary symptoms and progressive backache. What is the tumor marker, which can be indicative of disease relapse? 
Select and explain. 
A. CA 125, B. Beta-HCG, C. Carcinoembryonic antigen (CEA), D. PSA
D: PSA
Answer: D: PSA 
Explanation: Ans. is 'd' i.e. PSA The role of prostate specific antigen as a tumor marker for prostate carcinoma has been discussed in previous year question papers.