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 pill is useful in preventing all of the following except: \nSelect and explain. \nA. Carcinoma breast, B. Carcinoma ovary, C. Pelvic inflammatory disease, D. Anaemia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]