Are sand dunes constructive and destructive

A constructive force affects the earth's surface by building it up while forming new crust and landforms like mountains, islands, deltas, and sand dunes

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

read more on -

correct answer is a. and d.