This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of nail, Subject name: Dental
[{'content': 'In humans, nails grow at an average rate of ______ a month: \nSelect and explain. \nA. 1 mm, B. 3 mm, C. 5 mm, D. 7 mm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In humans, nails grow at an average rate of 3 mm (0.12 in) a month. Fingernails require three to six months to regrow completely, and toenails require twelve to eighteen months. Actual growth rate is dependent upon age, sex, season, exercise level, diet, and hereditary factors. Nails grow faster in the summer than they do in the winter.', 'role': 'assistant'}]