This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
Parietal cells in the stomach secrete a protein crucial for the absorp on of vitamin B12 by the ileum. What is this protein? 
Select and explain. 
A. Intrinsic factor, B. Gastrin, C. Somatostatin, D. Cholecystokinin (CCK)
A: Intrinsic factor
Answer: A: Intrinsic factor 
Explanation: .