Answer: The correct answer is C. Shallow areas.
Algae are simple plants living in damp areas or water. It is a simple non-flowering plant including sea weeds and other unicellular forms. Some algae contain the chlorophyll pigment but they lack proper roots, leaves, stems and the vascular tissues.
Algae naturally grow on water. Being photosynthetic plant algae also requires sunlight for undergoing the process of photosynthesis and hence live in shallow areas of sea floor where the sunlight reaches.