What Happens Immediately After a Signaling Molecule Binds to Its

What happens immediately after a signaling molecule binds to its G-protein coupled receptor (GPCR) ?

A) The signaling molecule enters the cell through its GPCR and travels to the nucleus,where it acts as a transcription factor.
B) The G protein exchanges GTP for GDP,and becomes inactivated.
C) The G protein exchanges GDP for GTP,and becomes inactivated.
D) The G protein exchanges GTP for GDP,and becomes activateD.
E) The G protein exchanges GDP for GTP,and becomes activated.