The Activation of Glucagon Receptors Turns the Liver into a Net

The activation of glucagon receptors turns the liver into a net producer of glucose.Glucagon stimulates a signal transduction pathway in liver involving:

A) SMAD protein phosphorylation.
B) Protein kinase A activation.
C) Calcium pumping into the endoplasmic reticulum.
D) Receptor tyrosine protein kinase activation.
E) Activation of G protein guanosine triphosphatase (GTPase) activity.