Although they were once classed together, archaea and bacteria have now been separated into two different domains. why was this change necessary?

a. the archaea only have cell membranes and the bacteria only have cell walls.
b. the two groups are composed of species with different cell sizes.
c. the archaea have nuclei and the bacteria do not.
d. the two groups replicate their dna in different ways.

Two groups replicate their DNA in different ways.

Explanation:

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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