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: Gynaecology & Obstetrics
[{'content': 'The effective sperm count normally is : \nSelect and explain. \nA. 20 million / ml, B. 30 million / ml, C. 40 million / ml, D. 50 million / ml', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 50 million / ml', 'role': 'assistant'}]