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': 'Vertical transmission of HIV is most likely to occur \nSelect and explain. \nA. Early antepartum, B. Late antepartum, C. Intrapartum, D. Postpartum', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Most of the vertical transmission of HIV is likely to occur during labor.', 'role': 'assistant'}]