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: Social & Preventive Medicine
Failure rate of contraceptive method is determined by ? 
Select and explain. 
A. Pearl index, B. Half life, C. Number of accidental pregnancies, D. Period of contraceptive practice continued
A: Pearl index
Answer: A: Pearl index 
Explanation: Ans. is 'a' i.e., Pearl index