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
[{'content': 'Progestase is effective for : \nSelect and explain. \nA. 1 year, B. 2 years, C. 4 years, D. 5 years', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 1 year', 'role': 'assistant'}]