Endosymbiosis can best be described as:

a

Two organisms occupying the same type of environment

b

Many cells of one type of organism living closely together

c

One organism living completely inside another organism

d

How a multicellular organism uses cell division to grow

I think the correct answer from the choices listed above is option C. Endosymbiosis can best be described as one organism living completely inside another organism. Symbiogenesis, or endosymbiotic theory, is an evolutionary theory which explains the origin of eukaryotic cells from prokaryotes.