To which trophic level do elk belong?
a. producer
b. decomposer
c. primary consumer
d. secondary consumer

C: primary Consumer

primary consumers are typically animals that eat plants aka herbivores.

producers would be plants

secondary consumers are typically ones that eat meat or eat meat and plants aka omnivores.

 decomposers, I believe are like your fungus or anything that feeds off of dead organisms or eat the waste of that organism.

Hopefully this helped. I  remember learning about this in college.  

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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i don't know. if i were you, i would search it up online : d