Monomeric G-proteins are activated when __(1)__ does __(2)__ and deactivated when __(3)__ does __(4)__
A) (1) GEF, (2) hydrolysis of GTP, (3) GAP, (4) binding to GTP
B) (1) GAP, (2) hydrolysis of ATP, (3) GEF, (4) binding to ATP
C) (1) GEF, (2) hydrolysis of ATP, (3) GAP, (4) binding to GDP
D) (1) GAP, (2) hydrolysis of GTP, (3) GEF, (4) binding to GTP