The correct answer is option C, Plankton
Reason -
In open ocean food web, the organism that lies at the bottom is planktons. Photo plankton consists of chlorophyll and is able to produce food of its own. The zoo planktons then feed on the photo planktons. Corals also survive by eating planktons. Small fishes survive by eating zooplanktons. Larges fishes then feed on smaller fishes. Thus, plankton is at the base of a complex aquatic food web.
