Which of the following is a possible pathological condition of the respiratory system?

The flu, or influenza, is a viral infection that primarily affects the respiratory system, specifically targeting the nose, throat, and sometimes the lungs. Symptoms often include fever, cough, sore throat, runny or stuffy nose, body aches, headaches, and fatigue, demonstrating its direct impact on respiratory health. This distinguishes it as a pathological condition specifically related to the respiratory system, as it involves inflammation and infection leading to various respiratory symptoms and complications.

In contrast, kidney stones, gallstones, and constipation are conditions affecting other systems in the body—renal, biliary, and gastrointestinal, respectively—making them unrelated to respiratory pathology.