Final answer:
The correct answer is C. esophagus. The esophagus is not a part of the respiratory system as it is involved in the digestive system.
Step-by-step explanation:
The correct answer is C. esophagus. The respiratory system consists of several organs involved in the process of breathing. The trachea, bronchi, larynx, and bronchioles are all parts of the respiratory system. However, the esophagus is not a part of the respiratory system. The esophagus is a long tube that carries food from the mouth to the stomach, and it is part of the digestive system.