Is the primary efferent neurotransmitter secreted by efferent axons of the cns.

The correct answer is "acetylcholine".

Acetylcholine is the primary efferent neurotransmitter of the central nervous system. Acetylcholine functions in the autonomic nervous system as a neurotransmitter in the autonomic ganglia of both parasympathetic and sympathetic nervous system. It also functions as the primary neurotransmitter for the parasympathetic nervous system. Acetylcholine also functions as the neurotransmitter released by motor neurons at the motor end plate to stimulate muscle excitation-contraction coupling. 

Photo means light and synthesis means combination so combination of light