What does the endosymbiotic theory propose that mitochondria in eukaryotic cells arose from?

How mitochondria evolved from bacteria

a
endosymbiotic prokaryotes that were photosynthetic
b
endosymbiotic eukaryotes that were photosynthetic
c
endosymbiotic prokaryotes that metabolized oxygen
d
endosymbiotic eukaryotes that metabolized oxygen

c) endosymbiotic prokaryotes that metabolized oxygen