The Hypothesis for the Origin of Eukaryotes Through Serial Endosymbiosis

The hypothesis for the origin of eukaryotes through serial endosymbiosis proposes that

A) the ancestors of mitochondria were aerobic heterotrophic prokaryotes, while the ancestors of plastids were photosynthetic prokaryotes.
B) mitochondria and plastids replicate in a manner similar to eukaryotes.
C) genes in mitochondria and plastids are similar to genes of ancient eukaryotes.
D) eukaryotes likely evolved from the fusion of small prokaryotic and small eukaryotic cells.