Answer: Sand on the ocean floor
Step-by-step explanation:
An ecosystem can be define as the biotic community where living beings interact with their non- living physical environment. It includes two components named as abiotic or non-living such as water, wind, sunlight, soil and others and biotic or living such as plants, microbes, animals and humans.
Among the options given, sand on the ocean floor is the correct option. This is because of the fact that sand is a kind of soil which is typically found near the sea shore and at the bottom bed of the ocean or seafloor. It is a non-living or abiotic factor of the marine ecosystem.