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: Surgery
[{'content': 'Investigation of choice for parotid gland calculi \nSelect and explain. \nA. Xray, B. USG, C. Sialography, D. CT', 'role': 'user'}, {'content': 'Answer: C \nExplanation: For submandibular gland calucli IOC is XRay as they are radio-opaque.\nFor parotid gland calucli IOC is sialography as they are radioluscent.', 'role': 'assistant'}]