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
Half life of IgG: March 2010 
Select and explain. 
A. 5 days, B. 6 days, C. 8 days, D. 23 days
D: 23 days
Answer: D: 23 days 
Explanation: IgG is a 150 kD monomer with a half-life of 23 days.