Which of the following is NOT a function of the respiratory system?

The function of the respiratory system primarily revolves around gas exchange, which includes the uptake of oxygen and the elimination of carbon dioxide. This exchange is vital for maintaining cellular respiration and metabolic processes in the body.

Regulation of blood pH is also a critical role of the respiratory system. By adjusting the rate and depth of breathing, the body can control the levels of carbon dioxide in the blood, which in turn influences the acidity (pH) of the blood.

Sound production is another key function, as the respiratory system facilitates phonation. Air moving through the vocal cords in the larynx allows for voice generation, enabling communication.

While the respiratory system has many important functions, the production of hormones is not one of them. Hormones are primarily produced by endocrine glands, and the respiratory system does not have a role in hormonal secretion or regulation. Thus, identifying it as a function not associated with the respiratory system is accurate.