The answer is A)mitochondria
The endosymbiotic theory explains that mitochondria and chloroplasts descended from the same type of bacteria. Symbiosis is an interaction between two organisms of different species, and endosymbiosis is a type of symbiosis in which one organism lives inside the other one. According to the endosymbiotic theory, a host cell ingested symbiotic bacteria, which specialised into mitochondria or chloroplasts. The evidence for this theory is that mitochondria and chloroplasts, like bacteria, have their own circular DNA. and They also have their own transcriptional and translational machinery.