I guess I would say b or d. Because concluded results change over time with better technology and some solutions dont work. 
        
                    
             
        
        
        
Answer:
 "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:
- Option - (a) is the best choice to choose from,
- <u>The refractory period :</u>
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.