One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis, facilitating erection. Since cGMP is inhibited, the signal is prolonged. The original signal that is now inhibited would have
A) hydrolyzed cGMP to GMP.
B) hydrolyzed GTP to GDP.
C) phosphorylated GDP.
D) dephosphorylated cGMP.
E) removed GMP from the cell.
Answer: A