Refer to the accompanying figure. What structure is designated by label B?

Refer to the accompanying figure. What structure is designated by label B?
  a. activation gate
  b. inactivation gate
  c. modulatory sensor
  d. transport pump
  e. transport sensor

Question 2

The accompanying figure represents a sequence of events occurring in the neuronal membrane (designated by the numbers 1 and 2). The letter I indicates an ion. What event is mostly likely being portrayed in this figure?
  a. activation of voltage-gated sodium channels
  b. activation of voltage-gated potassium channels
  c. activation of voltage-gated chloride channels
  d. activation of sodium-chloride pumps
  e. activation of sodium-potassium pumps