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
Following vasectomy, 
Select and explain. 
A. 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
C: Semen has to be analyzed till 2 consecutive sperm counts are zero
Answer: C: Semen has to be analyzed till 2 consecutive sperm counts are zero 
Explanation: Sterility following vasectomy is not immediate nor is its onset predictable. Thus another form of contraception is recommended until azoospermia is documented.