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': 'All of the following factors increases the density of X-ray except: \nSelect and explain. \nA. Increasing the kVp, B. Reducing the distance between focal spot and film, C. Decreasing the mA, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Factors that increase the density of X-ray:\n\nIncreasing the mA, KVp or exposure time increases the density.\nReducing the distance between focal spot and films also increases film density.\nDensity is inversely proportional to subject thickness and subject density due to beam attenuation.', 'role': 'assistant'}]