Which of the following statements is true?

aThe matter in an ecosystem must be continuously replenished.
bThe total amount of energy in an ecosystem remains the same.
cThe only way to return matter to the soil is decomposition.
dThe total amount of water in an ecosystem is always decreasing.

B. The total amount of energy in the ecosystem remains the same

Explanation:

Energy can not be created nor destroyed, therefore an ecosystem never "loses" or "creates" energy

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 correct answer is d