Which statement describes a function of mucus and cilia?

• A. Trap large particles
• B. Trap smaller particles/pathogens
• C. Exchange gases
• D. Produce hormones

Answer: (B)

Mucus and cilia work together to protect the airways through mucociliary clearance. Mucus, produced by goblet cells, is a sticky layer that traps inhaled particles and microorganisms. The cilia lining the airway beat in a coordinated rhythm to move this mucus upward toward the throat, where it can be swallowed or expelled. This system helps prevent pathogens and debris from reaching the lower airways and causing infection. Gas exchange happens in the alveoli and requires diffusion across membranes, not mucus/cilia, and hormones are produced by glands and endocrine tissues, not the airway lining. So the described function is trapping smaller particles and pathogens and then clearing them from the respiratory tract.