In an action potential, the permeability of sodium ions in the neurons increases due to:

Explanation

Option A mentions repolarization, which is the stage where there is a large influx of potassium ions out from the cell, during which sodium ions do not enter the cell. Option B mentions the concept of ionic bonding which is irrelevant to the scenario. Option C is correct, as when sodium voltage-gated channels open, only then does the permeability of sodium ions across the membrane increases, resulting in their influx into the cell. Option D describes an enzyme, that is important in recycling ACh across synapses; it is not relevant to the concept of sodium permeability during action potentials.