Question

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Answer 1

the mitochondrion is the place for ATP synthesis using the energy released during the redox reactions that occur in the internal membrane.

Answer 2

you are wright that A is correct. the electron transport chain performs redox reactions. it leads to the synthesis of ATP.
B is also correct if we consider the reverse reaction (usually not in play but possible in thermodynamic equilibrium:e.g. in case of excess ATP and blockade of the redox chain). but it is probably not the best description of the normal functioning of the system ;-)