The respiratory system facilitates coughing, sneezing, and other respiratory movements which help expel pathogens that are inhaled, thus preventing them from moving deeper into the body.

• A. The respiratory system uses coughing and sneezing to expel pathogens
• B. It uses gastric acid to kill pathogens in the stomach
• C. It filters blood through the lymph nodes
• D. It stores immune cells in the spleen

Answer: (A)

The main idea is that the respiratory system defends itself by reflexively expelling inhaled pathogens through coughing and sneezing. When the airways are irritated by irritants or microbes, coughing and sneezing generate strong airflows that physically push the particles out of the respiratory tract, preventing them from moving deeper into the body. Sneezing primarily clears the nasal passages, while coughing targets the lower airways, and together these reflexes form a rapid, mechanical way to remove invaders. Mucus trapping and cilia help by capturing pathogens and moving them toward the throat to be expelled, reinforcing this defense.

The option describing coughing and sneezing as mechanisms to expel pathogens directly matches this respiratory defense. Other choices point to different parts of the immune system—the stomach’s gastric acid, lymph nodes filtering lymph, or the spleen storing immune cells—that are not about expelling inhaled pathogens via respiratory movements.