An Early Step in the Evolution of Eukaryotic Cells Most

Multiple Choice

An early step in the evolution of eukaryotic cells most likely involved which of the following events?

A) endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into chloroplasts
B) endosymbiosis of a photosynthetic archaeal cell in a larger bacterial host cell to escape toxic oxygen-the anaerobic archaea evolved into chloroplasts
C) endosymbiosis of an oxygen-using bacterium in a larger bacterial host cell-the endosymbiont evolved into mitochondria
D) evolution of an endomembrane system and subsequent evolution of mitochondria from a portion of the smooth endoplasmic reticulum