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': 'Molar pregnancy is diagnosed best by \nSelect and explain. \nA. Clinical examination, B. Ultrasound, C. b hCG, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ultrasound', 'role': 'assistant'}]