What Explains Why the Magnitude of Transmitter Released from Nerve

Multiple Choice

What explains why the magnitude of transmitter released from nerve terminals decreases rapidly as the action potential amplitude is reduced form about 75 mV to about 45 mV?

A) The number of presynaptic sodium channels activated decreases.
B) The number of presynaptic potassium channels activated decreases.
C) The number of presynaptic calcium channels activated decreases.
D) The number of presynaptic chloride channels activated decreases.
E) The number of postsynaptic transmitter receptor channels activated decreases.