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': 'Prostaglandin used for cervical ripening? \nSelect and explain. \nA. PG E1, B. PG E2, C. PGF2 -a, D. Oral Oxytocin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: PG E2', 'role': 'assistant'}]