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
Pernicious anemia is due to - 
Select and explain. 
A. Iron deficiency, B. Atrophic gastritis, C. Low folic acid, D. None
B: Atrophic gastritis
Answer: B: Atrophic gastritis 
Explanation: None