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': 'Bag of membranes ruptures: \nSelect and explain. \nA. Before full dilatation of cervix, B. After full dilatation of Cx, C. After head is engaged, D. With excessive show', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Before full dilatation of cervix', 'role': 'assistant'}]