Which of these are tiny air sacs surrounded by capillaries where gas exchange occurs?

A) Bronchioles
B) Alveoli
C) Pleura
D) Cilia
E) Bronchi

Capillaries

The smallest blood vessels in the body, which facilitate the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste substances between blood and surrounding tissues.

Alveoli

Clusters of air sacs in which the exchange of gases between air and blood takes place; located in the lungs.

Bronchioles

A part of the respiratory tract that branches from the tertiary bronchi.