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': 'Following vasectomy, \nSelect and explain. \nA. Sterility is achieved immediately, B. Onset of sterility is predictable, C. Semen has to be analyzed till 2 consecutive sperm counts are zero, D. No need to use additional contraception after 1 month', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Sterility following vasectomy is not immediate nor is its onset predictable. Thus another form of contraception is recommended until azoospermia is documented.', 'role': 'assistant'}]