This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small Intestine Malabsorption disorders, Subject name: Pathology
Which one of the following is not a cause of vitamin B12 deficiency? 
Select and explain. 
A. Blind-loop syndrome., B. Dietary deficiency., C. Intrinsic factor deficiency., D. Resection of ascending colon.
D: Resection of ascending colon.
Answer: D: Resection of ascending colon. 
Explanation: - Vit B12 is absorbed from ileum; hence resection of ascending colon has nothing to do with Vit B12 deficiency - Vit B12 deficiency is caused d/t: | Intake | Absorption - d/t decreased intrinsic factor, pancreatic & ileal diseases, fish tape worm infection | Requirement - as in children, pregnancy, lactation, blind loop syndrome