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': 'Maximum increase in cardiac output occurs by what stage of pregnancy : \nSelect and explain. \nA. 10th week, B. 20th week, C. 30th week, D. At the onset of labour', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 30th week', 'role': 'assistant'}]