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: ENT
[{'content': 'Submaxillary calculi can be visualized by X-ray in: \nSelect and explain. \nA. 20% cases, B. 50% cases, C. 60% cases, D. 80% cases', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 80% of all salivary stones occur in the submanidbular glands because their secretions are highly viscous. 80% of submandibular stones are radiopaque and can be identified on plain radiograph.', 'role': 'assistant'}]