Final answer:
The pharynx is the part of the respiratory system that directs air and food into their proper channels and also assists in speech, making option B) pharynx the correct answer.
Step-by-step explanation:
The part of the respiratory system that routes air and food into their proper channels and plays a role in speech is the pharynx (B). The pharynx is a tube-like structure that performs numerous functions within the respiratory and digestive systems. It helps in conducting air from the nasal cavity through to the larynx, and directs food from the mouth to the esophagus. During swallowing, a flap called the epiglottis closes over the larynx to prevent food from entering the airway. On the other hand, the larynx, or 'voice box', is located below the pharynx and contains the vocal cords necessary for speech, but the larynx itself does not route air and food.