A volcano sends lava exploding into the air, creating extrusive ingenious rocks. Is this a fast or slow change?

It really depends on the location. If its underneath the earth and the magma will take a while to cool but if on surface, it should cool in a matter of days to weeks. In this situation yes because its going in the air and is gonna land on the ground which will cool pretty quickly.

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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answer; /// i believe the correct answer is (thrombocytopenia); (a)