To derive a^b*c, one can use either of the following two derivations:-
Derivation 1:
E ==> E ^ E
==> E ^ E * E
==> a ^ b * c
Derivation 2:
E ==> E * E
==> E ^ E * E
==> a ^ b * c
Draw a parse tree for both the derivations and do a postorder traversal of the same. The outputs would be a b ^ c* and a b c * ^. Only one of these is mentioned in the option and so that would be the answer. :)