Which of the following BEST describes what alveoli are?
AThey are the smallest tubes in the respiratory system.
BThey have a small amount of surface area.
CThey are found on the end of bronchioles.
DThey are comprised of millions of cells.
AThey are the smallest tubes in the respiratory system.
BThey have a small amount of surface area.
CThey are found on the end of bronchioles.
DThey are comprised of millions of cells.