As Regards Receptors Coupled to Gs (G-Stimulatory) and CAMP, Which

As regards receptors coupled to Gs (G-stimulatory) and cAMP, which of the following is false?

A) Binding of ligand to its receptor activates another distinct protein which catalyzes the displacement of GDP with GTP on the alpha Gs subunit.
B) The GTP?Gs alpha subunit dissociates from the beta/gamma subunits and activates adenylate cyclase.
C) Adenylate cyclase catalyzes the conversion of ATP to cAMP.
D) cAMP activates cAMP dependent protein kinase by binding to the regulatory subunits which causes dissociation of the regulatory subunits from the catalytic subunits.
E) The catalytic subunit of cAMP dependent protein kinase can phosphorylate proteins on serine.