Final answer:
Option A. An 18-month-old boy's repeated bronchitis is likely tied to compromised cilia function, which normally helps clear mucus and debris to prevent respiratory infections.
Step-by-step explanation:
The patient's history of bronchitis is most likely due to the effects of his disease on the cilia. Cilia are hair-like structures that line the respiratory tract and move in a wave-like fashion to help clear mucus and debris out of the airways, preventing respiratory infections. When cilia function is impaired, it can lead to repeated episodes of bronchitis because the body is less effective at clearing pathogens that cause respiratory illnesses.
The 18-month-old boy's repeated episodes of bronchitis and frequent diarrhea are most likely due to the effects of his disease on cilia. Cilia are tiny hair-like structures that line the respiratory tract and help move mucus and foreign particles out of the airways. When the cilia are damaged or not functioning properly, as in the case of chronic bronchitis, the airways become inflamed and mucus accumulates, leading to recurrent infections.