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': 'Compared with calcium tungstate screens, rare earth screens decrease patient exposure by about \nSelect and explain. \nA. 15%, B. 35%, C. 55%, D. 75%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Compared\xa0with\xa0the\xa0older\xa0calcium\xa0tungstate\xa0screens,\xa0rare\xa0earth\xa0screens\xa0decrease\xa0patient\xa0exposure\xa0by\xa055%\xa0in\xa0panoramic and cephalometric radiography.', 'role': 'assistant'}]