Answer: C. Epipelagic
The Epipelagic zone is the upper most layer of the ocean. It is the layer which receives maximum sunlight, because of availability of sunlight and nutrients like fresh oxygen and atmospheric carbon dioxide, this zone is suitable for active photosynthesis activity. This zone can sustain a large number of photosynthesizing organisms such as phytoplanktons. Phytoplanktons are small microscopic plant like organism which produce their own food by the process of photosynthesis. For example, diatoms.