Which Statement Correctly Describes the Meaning of the Value of DG

Which statement correctly describes the meaning of the value of DG ^$\circ$ _rxn for a reactant-favored reaction?

A) It is the amount of energy that is required to overcome the disorder of the system.
B) It is the amount of additional energy that must be supplied in order to initiate reaction.
C) It is the minimum amount of heat released from the system when reaction occurs.
D) It is the maximum amount of useful work obtainable from the reaction when it occurs.
E) It is the minimum amount of work which must be done on the system to make reaction occur.