This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Salivary Gland, Subject name: Surgery
[{'content': 'The diagnostic method of submandibular sialolithiasis is \nSelect and explain. \nA. USG, B. Sialography, C. Plain X-ray, D. CT scan', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) Plain X-rayRef: Bailey and Love 27th Edition Page 780* MC cause of Submandibular duct obstruction is Stones in Gland and Duct.* 80% stones are radio opaque and hence X ray is diagnostic.* 80% of salivary stones are seen in Submandibular duct.* Stones distal to Lingual nerve (Beyond 2nd Molar) - Duct lay opening and stone removal is enough', 'role': 'assistant'}]