The correct answer is capillaries. They are a type of blood vessel that facilitates the exchange of oxygen, carbon dioxide, nutrients, and waste products between blood and tissues.
The other options do not refer to blood vessels:
- Bronchi are air passages that lead from the trachea to the lungs.
- Alveoli are tiny air sacs in the lungs where gas exchange occurs.
- Cilia are microscopic hair-like structures on cells that help move substances across their surfaces.