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: Medicine
[{'content': 'The annual conversion rate to dementia in patients with mild congnitive impairment is - \nSelect and explain. \nA. 10%, B. 20%, C. 30%, D. 40%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]