Final answer:
Carbon dioxide is the gaseous waste product that exits the leaf through the stomata.
Step-by-step explanation:
In Biology, the gaseous waste product that exits the leaf through the stomata is carbon dioxide. Stomata are small openings on the surface of leaves that allow gases to be exchanged between the plant and its surroundings. During the process of photosynthesis, plants absorb carbon dioxide from the air through these stomata and release oxygen as a waste product.