Final answer:
The endosymbiont theory proposes that mitochondria and chloroplasts originated from prokaryotic cells establishing a symbiotic relationship within a eukaryotic host. Evidence supporting this theory includes the presence of circular DNA in mitochondria, similarities between bacterial and mitochondrial ribosomes, and mitochondrial division by binary fission. Hence the correct answer is option B
Step-by-step explanation:
The endosymbiont theory proposes that mitochondria and chloroplasts originated from prokaryotic cells establishing a symbiotic relationship within a eukaryotic host. Evidence supporting this theory includes the presence of circular DNA in mitochondria, similarities between bacterial and mitochondrial ribosomes, and mitochondrial division by binary fission. However, the absence of membrane-bound organelles in prokaryotes is not evidence for the endosymbiont theory.
Hence the correct answer is option B