Answer:
The correct answer would be A. the bacteria that live in the intestine of a rabbit.
Ecosystem can be defined as the interaction of living and non-living things in a particular area.
It is composed of two factors:
Biotic factors: These are the living organisms of the ecosystem. It includes all the plants, animals, and microbes living in a particular ecosystem.
Abiotic factors: These include all the non-living components of the ecosystem such as air, water, land, mountains, climate, nutrients et cetera.
These two factors interact with each other through energy flows and nutrient cycles.
As, bacteria and rabbit are the living organisms so, they form the biotic component of the ecosystem.