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: Pharmacology
Combined oral pill reduces the risk of: 
Select and explain. 
A. Breast cancer, B. Ovarian cancer, C. Cervical cancer, D. Vaginal cancer
B: Ovarian cancer
Answer: B: Ovarian cancer 
Explanation: None