The stomach, small intestine, and large intestine are all organs. When they work together to process food, they form a functional unit known as -

an organ system

an organism

a tissue

a cell

Organ system

Explanation:

All of them work within the digestive system

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 to your question is b