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': 'For a bitewing X-ray angulation of cone should be: \nSelect and explain. \nA. 10° above horizontal, B. 15° below horizontal, C. 10° below horizontal, D. 15° above horizontal', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]