What is the function and process of a neuron’s refractory period?

Physiologically, after an action potential has occurred, the sodium ions  channels are closed up momentarily.After this moment, no matter the extent of stimulation of the neuron,action potential will not be generated,(absolute refractive period) because the Voltage gated sodium channels will remain closed up.This intervals of non responsive of he action potential is called refractive period.it is the period for the plasma membrane to relax and prepare for another action potential propagation, provided the stimulus is greater than the normal stimulation for the neuron(relative refractive period)

Its duration depends on age groups, thus in  teenagers(18yrs)  about minutes and up to 20 hours in adults.

Its major significance it to ensure  animals adaptability and adjustment to a stimulus, so that the number of action  potential propagated  per minute is controlled.  Thus the length of the refractive period is a measure of the maximum frequency  of  transmission of action potential along a neuron.

Explanation:

answer: the correct option is d. enzyme

lactase and carbonic anhydrase are the examples of enzymes.

lactase is an enzyme, which is present in the small intestine of mammals. it in the digestion of the disaccharide, lactose ( milk sugar) by converting it into two monosachharide, which are glucose and galactose.

carbonic anhydrase is present in the red blood cells. this enzyme plays significant role in the transport of co₂. it in the conversion of co₂ and h₂o into carbonic acid, which is then dissociated into bicarbonate ions and hydrogen ions.