which taxonomic group of land plants, still in existence today, was the dominant group of land plants when the angiosperms began their rapid increase in speciation and distribution?

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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satellites are frequently used to make observations of the orbit on earth