Answer:
The correct answer is eukaryotes engulfed photosynthesizing prokaryotes
Step-by-step explanation:
The endosymbiotic theory or symbiogenesis is an evolutionary theory that traces the origin of eukaryotic cells from prokaryotic organisms. It explains that some of the organelles (Mitochondria and Chloroplasts) in eukaryotic cells evolved from free-living prokaryotic microbes which were ingested or engulfed. The ingested prokaryotic cells survived within the organism and developed a symbiotic relationship.
According to the theory, chloroplasts was formed when eukaryotes engulfed photosynthesizing prokaryotes and mitochondria was formed when bacteria capable of aerobic respiration were engulfed.