Common triggers of an asthma attack include all the following, EXCЕРТ:

A. Carbon dioxide; acidosis: Hypoventilation results in inadequate alveolar ventilation, causing retention of carbon dioxide (hypercapnia). Elevated CO₂ reacts with water to form carbonic acid, lowering blood pH and leading to respiratory acidosis. This is the primary physiological consequence of hypoventilation.

B. Oxygen; alkalosis: Hypoventilation does not cause increased oxygen retention, and alkalosis is associated with excessive CO₂ removal (hyperventilation), not retention. Oxygen levels may decrease slightly in hypoventilation, but the main effect is CO₂ accumulation.

C. Carbon dioxide; alkalosis: Retaining CO₂ lowers blood pH rather than raising it, so hypoventilation leads to acidosis, not alkalosis. The inverse relationship between CO₂ and pH explains this physiological effect.

D. Oxygen; acidosis: While hypoventilation may reduce oxygen levels, the acidosis that develops is due to CO₂ retention, not oxygen accumulation. Oxygen alone does not drive acid-base changes in this context.

E. Lactic acid; acidosis: Lactic acid contributes to metabolic acidosis during tissue hypoxia or anaerobic metabolism, but hypoventilation causes respiratory acidosis primarily through CO₂ retention, not lactic acid accumulation.

A. Alveoli: Alveoli are microscopic air sacs in the lungs where gas exchange occurs. They do not provide structural support to the trachea and have no role in keeping the airway open. Their function is strictly related to oxygen and carbon dioxide diffusion between the alveoli and pulmonary capillaries.

B. Epiglottis: The epiglottis is a flap of cartilage that covers the glottis during swallowing to prevent food from entering the airway. While it is cartilaginous, it does not maintain tracheal patency and is primarily a protective structure for the larynx.

C. Tracheal cartilage: The C-shaped tracheal cartilage rings provide rigidity to the trachea, preventing it from collapsing while allowing flexibility for the esophagus to expand during swallowing. These rings maintain the airway’s patency and structural integrity, ensuring continuous airflow to and from the lungs.

D. Vocal cords: Vocal cords (true vocal folds) are located in the larynx and are responsible for sound production. They do not provide structural support to the trachea or prevent its collapse, and their function is limited to phonation and regulating airflow through the glottis.