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
Compared with calcium tungstate screens, rare earth screens decrease patient exposure by about 
Select and explain. 
A. 15%, B. 35%, C. 55%, D. 75%
C: 55%
Answer: C: 55% 
Explanation: Compared with the older calcium tungstate screens, rare earth screens decrease patient exposure by 55% in panoramic and cephalometric radiography.