Once the "Threshold" for an Action Potential Is Reached What

Multiple Choice

Once the "threshold" for an action potential is reached what is the sequence of events that occur?
1) Potassium channels are activated and potassium ions move out of the neuron.
2) Sodium channels are activated and sodium ions move into the neuron.
3) The interior of the neuron becomes more negatively charged than the exterior.
4) The interior of the neuron becomes more positively charged than the exterior.

A) 1,3,4,2
B) 2,4,1,3
C) 4,1,2,3
D) 3,2,1,4