Which of the Following Manipulations Would Reduce the Release of Neurotransmitter

Multiple Choice

Which of the following manipulations would reduce the release of neurotransmitter from a presynaptic neuron terminal?
I. reduction in extracellular calcium ion concentration at the axon terminal
II. increase in extracellular sodium ion concentrations at the axon terminal
III. addition of tetrodotoxin to the extracellular fluid at the axon terminal

A) only I
B) only II
C) only III
D) only II and III
E) only I and II