Biology of Humans 4th Edition by Judith Goodenough,Betty McGuire

Exercise 13

In a healthy person, most of the particles that are inhaled into the respiratory system
a. are trapped in the mucus and moved by cilia to the pharynx (toward the digestive system).
b. pass through the alveoli into the circulatory system, where they are engulfed by white blood cells.
c. are caught on the vocal cords.
d. are trapped in the sinuses.