Answer:
The trachea divides into a left and right bronchus inside the lungs. These further separate into bronchioles, The tiniest bronchioles have tiny air sacs at their ends. They are known as alveoli. Thus, option B is correct.
Step-by-step explanation:
What is the role of trachea and alveoli?
The trachea splits into the right and left principal bronchi at the mediastinum at the level of the fifth thoracic vertebra.
The bronchi split off into progressively smaller channels before coming to an end in tiny air sacs known as alveoli.
During this process, oxygen diffuses from the alveoli to the blood through the alveolar walls' capillaries (small blood vessels).
Hemoglobin in red blood cells absorbs oxygen as it enters the bloodstream.
Therefore, trachea and alveoli in the respiratory system work together to allow gas exchange.