c. anaerobic bacteria.
Work Step by Step
According to the endosymbiotic theory, eukaryotic cells acquired mitochondria and plastids, including chloroplasts, by engulfing a free-living bacterium that developed a symbiotic relationship with its host cell. This process is referred to as endosymbiosis. Mitochondria were derived from the endosymbiosis of an aerobic bacterium. Therefore, mitochondria in protists originated from anaerobic bacteria which would be the answer c.