You are answering a USMLE-style medical question. Question: A 45-year-old woman with hypothyroidism comes to the physician because of progressive fatigue, lethargy, and epigastric pain after eating. Physical examination shows pale conjunctivae. Laboratory studies show decreased serum hemoglobin levels and increased serum gastrin levels. Esophagogastroduodenoscopy shows inflammation of the gastric body and fundus. A photomicrograph of a biopsy specimen taken from the gastric antrum is shown. Which of the following is the most likely cause of this patient's symptoms? Options: A) Mucosal cell hyperplasia B) Enterochromaffin-like cell hyperplasia C) Parietal cell destruction D) Chief cell destruction Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.