Final answer:
No action potential will occur following a subthreshold depolarization, as it does not reach the required threshold potential of -55 mV which is needed to generate an action potential.(option 3)
Step-by-step explanation:
After a subthreshold depolarization, no action potential will occur. Action potentials follow an "all or none" law, meaning they either happen completely, or they don't happen at all.
A subthreshold depolarization does not reach the critical threshold potential, which is typically around -55 mV. For an action potential to occur, this threshold must be crossed, leading to the opening of voltage-gated Na+ channels and a subsequent rapid depolarization of the neuron's membrane.
If the threshold is not reached, the neuron simply returns to its resting membrane potential without firing an action potential.