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': 'Target material used for generating X-rays: \nSelect and explain. \nA. Tungsten, B. Cobalt, C. Cadmium, D. Palladium', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Tungsten', 'role': 'assistant'}]