Which of the following BEST describes what alveoli are?

a. They are the smallest tubes in the respiratory system.

b. They are found on the end of bronchioles.

c. They have a small amount of surface area.

d. They are comprised of millions of cells.

Answer:- b. They are found on the end of bronchioles.

The correct answer is ‘They are found on the end of bronchioles.’ Alveoli are tiny air sacs found at the end of bronchioles. They are comprised of millions of cells and have a large surface area, which allows for the efficient exchange of gases between the lungs and the bloodstream.