Answer: C. bacteria
Step-by-step explanation:
A biosphere is a part of earth where life exists. It consists of living beings which interact with other spheres of earth like atmosphere, hydrosphere, and lithosphere. It involves cycling of matter and energy.
Bacteria is the correct option as it is a living being belonging to the group of prokaryotes. It does not posses nucleus. It does not posses membrane bound organelles. The genetic material is in the form of DNA. It can live as an infectious agent in the body of host like plants, animals or human.