Asecond action potential cannot be generated until
a) the membrane potential has been reestablished
b) the na ions have been pumped back into the cell
c) proteins have been resynthesized
d) all sodium gates are closed

"Action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern."

It is the mode through which a neuron transports electrical signals.

Explanation:

A second action potential cannot occur until the membrane has recovered or reestablished, this is the refractory period. The absolute refractory period coincides with inactivation of voltage-gated sodium channels which makes it impossible to generate another nerve impulse.

"a.) well–developed vascular system."