What is the primary function of a neuron?

The primary function of a neuron is to receive messages from the senses and then respond with motor activity such as a finger being burnt and thpe arm muscle pulling the finger out of harms's way. So safety is part of it. Another function is to use sensory neurons to evaluate a scientific understanding of the world, such as determining which mineral is being looked at ie by its' colour, hardness, crystal system etc.

The Answer is D : When tryptophan is present at high concentrations, the repressor binds to the operator and transcription is initiated and not terminated.

                   

             -Hope this helped!