The Endosymbiotic Theory proposes that the organelles distinguishing eukaryote cells evolved through symbiosis of individual single-celled prokaryotes. Refer to the diagram provided. What is the BEST explanation for what is happening in step C?
A) A bacterial cell is engulfing a mitochondria from its environment.
B) A cell engulfs a cyanobacteria cell, without digesting it, allowing it to become an endosymbiont, producing sugars within the cell.
C) A prokaryotic cell engulfs other prokaryotic cells allowing the cell to become more complex, incorporating the new cells' organelles.
D) A cell engulfs an aerobic bacterial cell, without digesting it, allowing it to become an endosymbiont, giving the cell a survival advantage.