Question

the two gases that are constantly being exchanged in the respiratory system are and

Explanation:

The respiratory system is responsible for gas exchange. Oxygen ($O_2$) is taken in from the air, which is essential for cellular respiration to produce energy. Carbon dioxide ($CO_2$) is a waste product of cellular metabolism and is exhaled out of the body. This exchange occurs in the alveoli of the lungs.

Answer:

Oxygen and Carbon dioxide