A. Oropharynx: The oropharynx is the middle part of the throat behind the mouth. It is the primary pathway food must travel through to reach the esophagus; therefore, it cannot be blocked during swallowing. B. Nasopharynx: This must be blocked by the soft palate and uvula to prevent food and liquids from entering the nasal cavity. C. Larynx: The larynx must be blocked by the epiglottis to prevent food from entering the "windpipe" and causing choking. D. Mouth: The tongue blocks the front of the mouth during the "oral stage" of swallowing to ensure food moves backward into the throat rather than forward out of the lips.