In which zone can rooted plants be expected to be found attached to the seafloor? what is the name of this zone, and why are plants found there?

Hello!

The answer you're looking for is the Benthic zone:

The Benthic zone is the region at the lowest level on an ocean or lake, including the seabed. In this zone is where plants can attach themselves to the ocean floor if the water is shallow enough for the sunlight to reach them. Some plants that can be found in the Benthic zone include:

-Eel Grass
-Mangroves
-Turtle Grass
-Cattails