A 45-year-old male presents to the ED complaining of chest pain and drooling that staed immediately after eating a steak. His past medical history is significant for ingestion of a caustic solution, 5 years ago . On physical examination, patient can talk normally and breaths without effo. He is drooling. The chest pain is vague and constant. A chest X-ray shows no subcutaneous emphysema. An endoscopy confirms the presence of a retained bolus of meat 25 cm beyond the incisors where a stricture is identified. The bolus is removed and the stricture is dilated. Which of the following anatomic spaces contains the stricture