For sodium to accumulate rapidly in a neuron,

For sodium to accumulate rapidly in a neuron,
  a. a stimulus above the threshold must open
  sodium gates in an accelerating manner.
  b. the wave of repolarization must occur to
  reestablish a resting potential.
  c. there must be a dramatic increase in the negative
  charge of the cytoplasm.
  d. a voltage surge must cause the sodium gates to
  close.
  e. the potassium gates must first open.

Question 2

Active transport
  a. helps establish the resting potential of a neuron.
  b. counters the process of diffusion.
  c. allows transport of ions across the plasma
  membrane of the neuron against the
  concentration gradient.
  d. helps establish the resting potential of a neuron
  and counters the process of diffusion.
  e. does all of these.