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: Physiology
Receptor for absorption of Vit-B12 intrinsic factor complex is located in 
Select and explain. 
A. Ileum, B. Duodenum, C. Transverse colon, D. Descending colon
A: Ileum
Answer: A: Ileum 
Explanation: For the absorption of Vit B12, it has to form a complex with Intrinsic factor. This complex has a receptor on the epithelial cell surface of ileum. Once attached, the complex is absorbed.