The G protein coupled receptor (GPCR) pathway elicits diverse intracellular responses in different cells. The basic steps of GPCR signaling are outlined in this diagram. Which of the following statements correctly describes the process of GPCR signaling?

A) The GPCR activation is reversible after the signal of the ligand diminishes.
B) The membrane-embedded enzyme uses GTP as a secondary messenger to initiate gene expression.
C) The ligand attaches to both the GPCR and the membrane-embedded enzyme to activate the GPCR pathway.
D) The ligand-bound GPCR sends a GTP molecule to an enzyme in the membrane and switches it into an active state.