Final answer:
Submerged aquatic plants lack stomata, which regulate the exchange of gases and water vapor with the environment.
Step-by-step explanation:
Submerged aquatic plants lack stomata, which are openings on the surface of leaves and stems that regulate the exchange of gases and water vapor with the environment.
Since these plants live underwater, they do not need to regulate their water loss through stomata as much as terrestrial plants do. Instead, they have adapted to absorb gases directly from the water.
Therefore, the correct answer is C) stomata.