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': 'Which radiographic projection is most useful in examining stone of a submandibular duct \nSelect and explain. \nA. Cross-sectional occlusal, B. OPG, C. Lateral oblique, D. PA view of mandible', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]