The lung is made up of a complex network of air passages that facilitate respiration. This network comprises the bronchi, bronchioles, and alveoli. The bronchi are the two main air passages that branch off from the trachea and carry air into the lungs. The bronchioles are smaller branches of the bronchi that further divide into tiny air sacs called alveoli. The alveoli are the primary sites of gas exchange, where oxygen from the air is taken up by the bloodstream and carbon dioxide is released from the bloodstream into the air. Therefore, option C is the correct answer.