You are answering a USMLE-style medical question. Question: A 35-year-old man comes to the physician because of episodes of difficulty swallowing for the past 3 months. He feels solid food getting stuck in his chest behind the sternum when he eats. Drinking does not cause any difficulty swallowing. He has no coughing or nasal regurgitation. He has no hoarseness or weight loss. He has had heartburn for 2 years with no response to high-dose omeprazole. His past medical history is also significant for asthma and eczema. He takes no medications except for omeprazole. His vital signs are within normal limits. Physical examination shows no abnormal findings. Which of the following best explains these findings? Options: A) Achalasia B) Diffuse esophageal spasm C) Eosinophilic esophagitis D) Esophageal reflux disease Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.