Which term refers to environments based in water?

The term that refers to environments based in water is "aquatic." This classification encompasses various ecosystems such as oceans, rivers, lakes, and wetlands. Aquatic environments are characterized by their wet conditions and the presence of water, which shapes the types of organisms that can thrive there, including fish, amphibians, aquatic plants, and other life forms specifically adapted to living in or near water.

In contrast, "terrestrial" pertains to land-based environments, making it distinct from aquatic habitats. The terms "flora" and "fauna" relate more to the plant life and animal life, respectively, within any environment, whether terrestrial or aquatic. Therefore, the correct answer specifically highlights the water-based nature of the environments being discussed.