Answer:
Rods and Cone can best fill in the spaces.
Explanation:
Bipolar cells exist between photoreceptors (rod cells and cone cells) and ganglion cells. They act, directly or indirectly, to transmit signals from the photoreceptors to the ganglion cells.
Bipolar cells receive synaptic input from either rods or cones, or both rods and cones, though they are generally designated rod bipolar or cone bipolar cells. There are roughly 10 distinct forms of cone bipolar cells, however, only one rod bipolar cell, due to the rod receptor arriving later in the evolutionary history than the cone receptor.
In the dark, a photoreceptor (rod/cone) cell will release glutamate, which inhibits the ON bipolar cells and excites (depolarizes) the OFF bipolar cells. In light, however, light strikes the photoreceptor which causes the photoreceptor to be inhibited (hyperpolarized) due to the activation of opsins which activate All trans-Retinal, giving energy to stimulate G-Protein coupled receptors to activate phosphodiesterase (PDE) which cleaves cGMP into 5'-GMP. That is the mechanism of reaction.
