With Regard to the Process of Neural Transmission,a Refractory Period

With regard to the process of neural transmission,a refractory period refers to a time interval in which

A) a neuron fires more rapidly than usual.
B) an electrical charge travels from a sensory neuron to a motor neuron.
C) positively charged sodium ions are pumped back outside a neural membrane.
D) an individual reflexively withdraws from a pain stimulus.