During Signal Transduction That Involves Heterotrimeric G Proteins, the Event

During signal transduction that involves heterotrimeric G proteins, the event that immediately precedes the dissociation to alpha monomer and beta-gamma dimer is the

A) binding of a hormone ligand to the intact heterotrimer.
B) creation of new protein-protein interactions.
C) exchange of guanine nucleotides on the alpha subunit.
D) hydrolysis of guanosine triphosphate by the beta subunit.
E) posttranslational modification of the gamma subunit with a lipid anchor.