This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Natural Methods, Barrier Methods, IUDs, OCPs, Subject name: Social & Preventive Medicine
In basal body temperature method, after the rise of temperature, the unsafe period lasts for :- 
Select and explain. 
A. 24 hours, B. 48 hours, C. 72 hours, D. 120 hours
C: 72 hours
Answer: C: 72 hours 
Explanation: - In BBT, the rise of temperature signifies ovulation. - Since maximum survival of ovum post ovulation is 3 days, the unsafe period is 3 days post rise of body temperature. Other natural methods of contraception are: Calender method / feile period method/ safe period method/ rhythm method Cervical mucus method Symptothermic method Coitus interruptus Abstinence - most effective method