Shown Here Are Four Ligands (M, H, K, and L)

Multiple Choice

Shown here are four ligands (M, H, K, and L) and their corresponding receptors along with four genes (S, T, U, and V) whose activity the receptor controls through signal transduction. The arrows indicate gene activation, the T-bars indicate gene repression. Which ligand acts as a signal resulting in both genes U and V being active?

A) ligand M
B) ligand H
C) ligand K
D) ligand L
E) None of the answer options is correct.