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
Rich source of IgG is: 
Select and explain. 
A. Stomach, B. Visceral peritoneum, C. Small intestine, D. Large intestine
C: Small intestine
Answer: C: Small intestine 
Explanation: C i.e. Small intestine (Most probably) Most abundant immunoglobin in blood --> IgG.