What effect would a chemical that blocks the voltagegated sodium ion channels in the excitable axon membrane of a neuron have on its ability to depolarize?

During the refractory period a) if a neuron reaches threshold the action potential goes to completion b) No stimulus of any strength will trigger a new action potential c) It is possible to trigger a new action potential but only with an unusually strong stimulus d) The signal grows weaker with distance e) The neuron fires at its maximum voltage if a stimulus depolarizes the neuron to threshold

Imagine a neuron that has a thousand axonal terminals synapsing on it. The majority of these axonal knobs are shown to be "firing." However, the neuron in question does not fire an action potential. What could be a possible explanation as to why this could be?

What events in a neuron membrane occur slowly when threshold potential is reached?   Opening of K+ channel activation gate   Closing of Na+ channel inactivation gate   Opening of the Na+ voltage-gated channel activation gate   Closing of Cl- voltage gated channels   Closing of K+ inactivation gate (More than one answer may be correct, please help in answering)