Certain Protozoa Engulf Cyanobacteria (Photosynthetic Bacteria)and Maintain a Given Number

Certain protozoa engulf cyanobacteria (photosynthetic bacteria) and maintain a given number of the cyanobacteria even when they divide.The protozoa divide only after the cyanobacteria have doubled their number.The cyanobacteria excrete glucose that the protozoa use for energy.This is a good example of

A) parasitism by protozoa.
B) how protozoa consume particulate food.
C) establishment of an endosymbiotic relationship.
D) symbiosis between two microorganisms.
E) convergent evolution.