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': 'Which of the following crystal is mostly present in X-ray\nfilm? \nSelect and explain. \nA. KBr, B. KI, C. AgBr, D. AgI', 'role': 'user'}, {'content': 'Answer: C \nExplanation: X-ray film has two principal components: (1) emulsion and (2) base. The emulsion, which is sensitive to X-rays and visible light, records the radiographic image. The base is a plastic supporting material onto which the emulsion is coated.\xa0\nThe two principal components of emulsion are silver halide grains, which are sensitive to X-radiation and visible light, and a vehicle matrix in which the crystals are suspended. The silver halide grains are composed primarily of crystals of silver bromide.', 'role': 'assistant'}]