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: Radiology
[{'content': 'Investigation of choice for locating Parathyroid gland: \nSelect and explain. \nA. Tc Thallium substraction scan, B. CAT Scan, C. USG, D. Angiography', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Tc-Thallium Substraction Scan', 'role': 'assistant'}]