Final answer:
The mitochondria are the organelles in bacteria related to energy metabolism and are thought to originate from a bacterial endosymbiotic event, consistent with the Endosymbiotic Theory. The correct option is A.
Step-by-step explanation:
The organelle in bacteria that holds the property of energy (E) metabolism, originally obtained from a bacteria it engulfed, is mitochondria. According to the Endosymbiotic Theory, first proposed by Lynn Margulis, mitochondria and chloroplasts are thought to have evolved from endosymbiotic events involving an ancestral eukaryotic cell and a prokaryotic cell.
These organelles contain their own DNA, similar to that of prokaryotes, and the double membrane of the mitochondria is consistent with this endosymbiotic origin: the outer membrane being eukaryotic and the inner membrane being prokaryotic in nature.
Moreover, the infoldings in the inner mitochondrial membrane, known as cristae, resemble the outer surface of alpha-proteobacteria, which supports this theory further.