The C in COPD stands for:

A. Hemoglobin is an iron-containing protein found in red blood cells. It binds to oxygen in the lungs and carries it through the bloodstream to tissues throughout the body.
B. Antigens are substances that can trigger an immune response, but they are not involved in carrying oxygen in the blood.
C. Albumin is a protein in the blood that helps maintain osmotic pressure and transports various substances, but it does not carry oxygen.
D. Bicarbonate ions are involved in carbon dioxide transport in the blood, not oxygen. They help regulate the pH of blood and facilitate CO₂ transport from tissues to the lungs.

A. Crackles are discontinuous, short popping sounds that are often heard during inhalation and are typically associated with conditions like pneumonia or pulmonary edema, not asthma.
B. Wheezes are continuous, high-pitched sounds often heard during exhalation and are commonly associated with asthma or other obstructive airway conditions. These sounds are caused by the narrowing of the airways.
C. Stridor is a harsh, high-pitched sound often heard during inhalation and indicates upper airway obstruction, such as in croup or a foreign body in the airway.
D. Rhonchi are low-pitched, gurgling sounds that are often associated with blockages in the larger airways (such as mucus) and are generally heard during both inhalation and exhalation, but they are not typically high-pitched like wheezes.