A) Hypercapnia. Hypercapnia refers to an excessive amount of carbon dioxide in the bloodstream, typically due to hypoventilation. B) Hypoxemia. Hypoxemia is a condition characterized by low oxygen levels in the blood, specifically the arterial blood. C) Dyspnea. Dyspnea refers to a subjective sensation of difficulty or uncomfortable breathing. D) Hypoxia. Hypoxia refers to a deficiency of oxygen in the tissues, not specifically in the blood.