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
Pearl Index is a measure of : 
Select and explain. 
A. Potency of contraceptives, B. Feility rate, C. Potency of disinfectant, D. Couple protection rate
A: Potency of contraceptives
Answer: A: Potency of contraceptives 
Explanation: Potency of contraceptives