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': 'Investigation of choice to detect Hydatiform mole is : \nSelect and explain. \nA. X-ray abdomen, B. USG, C. Serum HCG level, D. Gravindex', 'role': 'user'}, {'content': 'Answer: B \nExplanation: USG', 'role': 'assistant'}]