Annual fluctuations in atmospheric carbon dioxide concentrations occur because A. Plants in the northern hemisphere lose their leaves during the winter
B. CO2 emissions increase in the winter
C. Humans influence CO2 concentrations
D. Photosynthesis stops at night while respiration continues

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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the answer is: metamorphic rocks often show the presence of fossils, also a

hope i

-lavira: )