9. What are groups of similar cells that work together to perform a specific function called? (1 point) A organ system
B organ
C cells
D tissues

D tissues

hope u got the answer

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 trees if i'm not mistaken