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
"Oral contraceptive pills" protect against: 
Select and explain. 
A. Thrombosis, B. Ovarian cancer, C. Cancer cervix, D. Hepatocellular adenoma
B: Ovarian cancer
Answer: B: Ovarian cancer 
Explanation: None