Does sound travel at the same speed through all materials

no

Explanation:

Sound travels fastest in liquid than in air and than in solid

Water> Air> Solid

Hope it helps :)

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.  

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