Hakeen is testing the effects of sunlight on samples of soil. Which of these actions would introduce confounding variables into Hakeems experiment? A. He tests a theory that’s already been established.
B. He tests multiple hypothesis at a time.
C. He uses identical specimens when completing multiple trials.
D. He adjusts the independent variable and records the effects.
E. He uses different types of soil in each of his samples.

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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