This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Salivary Glands, Subject name: Surgery
[{'content': 'What % of submandibular salivary gland stones are radiopaque? \nSelect and explain. \nA. 10%, B. 70%, C. 80%, D. 90%', 'role': 'user'}, {'content': "Answer: C \nExplanation: 80% of submandibular salivary gland stones are radiopaque. SIALOLITHIASIS 80% of all salivary gland stones occur in submandibular glandQ, 10% occur in parotid, 7% in sublingual and the remainder in minor salivary glands. MC site is Whaon's ductQ > submandibular gland substance Composition of stone: Calcium and magnesium phosphate or carbonateQ Due to deposition of calcium salts, 80% stones are radio opaqueQ", 'role': 'assistant'}]