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
Billing's method of contraception refers to: 
Select and explain. 
A. Monitoring BBT, B. Cervical mucus method, C. Rhythm method, D. Coitus interruptus method
B: Cervical mucus method
Answer: B: Cervical mucus method 
Explanation: None