Final answer:
Photoreceptors release glutamate to induce hyperpolarization.
Step-by-step explanation:
The correct answer is c) Glutamate. Photoreceptors release glutamate to induce hyperpolarization. When light strikes rhodopsin, a G-protein called transducin is activated, which in turn activates phosphodiesterase. This enzyme converts cGMP to GMP, closing sodium channels and causing the membrane to become hyperpolarized. As a result, glutamate is not released to the bipolar cell.