A Postsynaptic Neuron Has Three Presynaptic Inputs - from Neurons

Multiple Choice

A postsynaptic neuron has three presynaptic inputs - from neurons X,Y and Z.When X and Y are stimulated simultaneously and repeatedly,the postsynaptic neuron reaches threshold and undergoes an action potential.When X and Z are stimulated simultaneously,however,there is no change in the membrane potential of the postsynaptic neuron.What can you tell about presynaptic neurons Y and Z?

A) They are probably both excitatory
B) They are probably both inhibitory
C) Y is probably excitatory and Z is probably inhibitory
D) Z is probably excitatory and Y is probably inhibitory