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
Which of the following has LEAST pregnancy failure rate : 
Select and explain. 
A. OCP, B. IUCD, C. Diaphragm, D. Condom
A: OCP
Answer: A: OCP 
Explanation: OCP