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
Complement C1 is produced by 
Select and explain. 
A. Macrophages, B. Liver, C. Intestinal epithelium, D. Spleen
C: Intestinal epithelium
Answer: C: Intestinal epithelium 
Explanation: C1 - Intestinal epithelium
C2, C4 - Macrophages
C5, C8 - Spleen
C3, C6, C9 - Liver