The electron transport chain is made up of four segments (Complexes I-IV with O2 as the final electron acceptor). Which statement best describes the electron transport chain
选项：

A:Each component involves a phosphorylation step.
B:Each complex directly transfers electrons to O2.
C:Electrons flow spontaneously from one carrier to the next.
D:Fe-S cluster acts as a important coenzyme in complex.
E:Locate in outer membrane of mitochondria