求一生物高手兼英语能人给瞅瞅这道题怎么解?

求一生物高手兼英语能人给瞅瞅这道题怎么解?
According to the endosymbiotic theory of the origin of eukaryotic cells,how did mitochondria originate?
A.by secondary endosymbiosis
B.when a protoeukaryote engaged in a symbiotic relationship with a protobiont
C.from the nuclear envelope folding outward and forming mitochondrial membranes
D.from infoldings of the plasma membrane,coupled with mutations of genes for proteins in energy-transfer reactions
E.from engulfed,originally free-living prokaryotes
我的分已经用完了,