Final answer:
Additional action potentials can occur after the absolute refractory period, but during the relative refractory period, a stronger stimulus is required. Ultimately, more action potentials can be generated once both the absolute and relative refractory periods are complete.
Step-by-step explanation:
When a neuron receives a prolonged stimulus that is just above the threshold level, additional action potentials can be produced once the membrane has completed the absolute refractory period. During this time, due to the inactivation gate of the voltage-gated Na+ channel, no new action potentials can occur. However, once the absolute refractory period has passed and the membrane potential has returned to near its resting level, an action potential can be initiated by a stronger stimulus than the one that initiated the current action potential. This is due to the relative refractory period, when the voltage-gated K+ channels have not yet closed, leading to a heightened threshold for initiating another action potential. Considering the options provided and the information on how the relative refractory period requires a stronger stimulus, you would expect to get additional action potentials when the membrane has completed the absolute and relative refractory periods.