<prompt> An old man having complaint of anorexia, weakness and paraesthesia. On investigation, his haemoglobin was 5.8g and peripheral smear showed macrocytes and neutrophils having hypersegmented nuclei. His tendon reflexes were also sluggish. Endoscopy revealed atrophic gastritis. Deficiency of which of the following factor can lead to this situationFolic acidRiboflavinVitaminB12None  <response>: Diagnosis of the patient is pernicious anemia. Factors favouring this diagnosis are:Megaloblastic anemia.Demyelination decreased tendon reflexesAtrophic gastritisSo, he would require B12 supplementation. 