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: Dental
[{'content': 'A 12 year old male patient wants to undergo orthodontic treatment as he feels his upper incisors are too prominent. He is advised a pre-treatment lateral cephalogram. What is the value of distance ‘A’ ? \nSelect and explain. \nA. 4 feet, B. 50 inches, C. 6 feet, D. 60 inches', 'role': 'user'}, {'content': "Answer: D \nExplanation: Diagrammatic representation of the American standard cephalometric arrangement. By convention, the distance from the X-ray source to the subject's midsagittal plane is 5 feet (60 inches). The distance from the midsagittal plane to the cassette can vary in many machines, but must be the same for each patient every time.", 'role': 'assistant'}]