Considering the endosymbiotic theory, which of the following findings provides the strongest evidence for the bacterial origin of mitochondria?
Correct: B
While all options present similarities, the presence of circular DNA (like bacterial chromosomes) and 70S ribosomes (characteristic of prokaryotes) within mitochondria provides the strongest molecular evidence for their bacterial origin. Eukaryotic cytoplasm contains 80S ribosomes. The shared use of ATP and oxidative phosphorylation are functional similarities, and binary fission and size are morphological/physiological similarities, but the unique molecular machinery of DNA and ribosomes is a more fundamental indicator of common ancestry, as these are core components of genetic information processing and protein synthesis.