This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Prostate and seminal vesicles, Subject name: Surgery
[{'content': 'Normal level of PSA in males is: \nSelect and explain. \nA. < 4ng/dl, B. 4-10 ng/ml, C. >10 ng/ml, D. <4 ng/ml', 'role': 'user'}, {'content': 'Answer: D \nExplanation: PROSTATE SPECIFIC ANTIGEN (PSA) -- Causes liquefaction of seminal coagulum. Normal value <4ng/ ml (In > 50 years); Value > 20ng/ml diagnostic of CA prostate. PSA is the single test with highest positive reactive value for CA prostate. PSA is prostate specific, not the cancer specific. Level of PSA Is directly related to tumor burden.', 'role': 'assistant'}]