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': 'The most diagnostic sign of pregnancy is : \nSelect and explain. \nA. Amenorrhoea, B. Quickening, C. Foetal hea sounds, D. Distention of abdomen', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Foetal hea sounds', 'role': 'assistant'}]