Final answer:
The alveoli, which are crucial for gas exchange, are located in the lungs, making them the organs of the respiratory system that contain alveoli.
Step-by-step explanation:
The organ(s) of the respiratory system that contain alveoli are the lungs. The respiratory system includes various structures such as the pharynx, larynx, trachea, and bronchi, which are all significant for the process of breathing. However, the alveoli are specifically found in the lungs. Gas exchange, which is the primary function of the respiratory system, occurs within the alveoli where oxygen from the inhaled air is exchanged with carbon dioxide from the blood in the surrounding capillaries. Thus, the correct answer to the question is 1) Lungs.