An abnormal decrease in the depth and rate of respiration is termed:

A. Effusion refers to the accumulation of fluid in the pleural space, not a substance that reduces surface tension in the alveoli.
B. Bicarbonate is an important component in the buffering system of the blood, but it does not reduce surface tension in the lungs.
C. Exudate is fluid that leaks out of blood vessels due to inflammation or injury, often seen in conditions like pneumonia or pleuritis, but it does not affect surface tension in the alveoli.
D. Surfactant is a lipid-protein mixture produced by type II alveolar cells in the lungs. It reduces surface tension in the alveoli, preventing the lungs from collapsing and making it easier to breathe.

A. Asthma is commonly associated with allergic responses, especially allergic asthma, which is triggered by allergens like pollen, dust mites, or pet dander.
B. Allergic rhinitis is an allergic reaction that affects the nasal passages, typically caused by airborne allergens.
C. Hay fever is another term for seasonal allergic rhinitis, directly linked to allergens such as pollen.
D. Acute coryza, also known as the common cold, is caused by a viral infection (most commonly rhinovirus), not an allergic reaction. While symptoms may be similar to allergic rhinitis, the underlying cause is infectious, not immunologic hypersensitivity.