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
For cephalometric projection, what should be the distance between source and the subject? 
Select and explain. 
A. 5 feet, B. 6 feet, C. 7 feet, D. 9 feet
A: 5 feet
Answer: A: 5 feet 
Explanation: Distance between source and the subject = 5 feet.
Distance between film and the subject = 15 cm.