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
[{'content': '"Oral contraceptive pills" protect against: \nSelect and explain. \nA. Thrombosis, B. Ovarian cancer, C. Cancer cervix, D. Hepatocellular adenoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]