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 O
C:Electrons flow down the potetial difference from one carrier to the next.
D:Every complex has an Fe-S cluster.
E:FADH2 chain is the main main to produce H2O