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: Social & Preventive Medicine
[{'content': 'True statements of Nova-T \nSelect and explain. \nA. Effective for 10 years, B. More copper content, C. More chances of perforation, D. Silver core', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]