Question

lo 4.3. what is the respiratory system responsible for?
maintenance of acid - base balance
exchange of gases
regulation of body temperature
transportation of nutrients
production of hormones

Explanation:

The respiratory system's main function is gas exchange. It takes in oxygen ($O_2$) from the air and releases carbon dioxide ($CO_2$) from the body. While the respiratory system can have some minor indirect roles in acid - base balance (through $CO_2$ levels which affect blood pH), its primary and most direct role is gas exchange. The regulation of body temperature is mainly by the integumentary system (e.g., sweating), the transportation of nutrients is a role of the circulatory system, and the production of hormones is mainly by the endocrine system.

Answer:

Exchange of gases