Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?
a. receptor tyrosine kinase
b. g protein-coupled receptor
c. ligand-gated ion channel
d. intracellular receptor

c. ligand-gated ion channel

Explanation:

As soon as a signaling molecule binds a ligand-gated ion channel it leads to the opening of these ion channels which in turn causes ions to either rush inside or outside of the cell on which they are located leading to the disruption of distribution of initial ion concentration.  

As the name suggests, these kind of receptors are also known as ionotropic receptors.

For example: Binding of acetylcholine hormone to it's receptor which is a ligand gated cation channel located at post synaptic muscle cells leads to the opening of Na⁺ ion channels. As a result of this, Na⁺ rushes into muscle cell leading to the change in the concentration of Na⁺ inside the muscle cells. This is known as depolarisation.

im not intirely sure but i think the anwser is d relative humidity