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: Microbiology
[{'content': 'Half life of IgG: March 2010 \nSelect and explain. \nA. 5 days, B. 6 days, C. 8 days, D. 23 days', 'role': 'user'}, {'content': 'Answer: D \nExplanation: IgG is a 150 kD monomer with a half-life of 23 days.', 'role': 'assistant'}]