An INHIBITORY signal is sent between neurons when rushes into the neuron.

A. Na+
B. K+
C. Cl-
D. Ca-

An INHIBITORY Signal is sent between neurons when (A)Na+ rushes into the neuron.

Explanation:

When one spot of membrane supports an action potential, lots of \text {Na}^+Na+start text, N, a, end text, start superscript, plus, end superscript ions hurry into the cell by that spot. These ions radiated out sideways into the cell and can depolarize a nearby spot of membrane, stimulating the hole of voltage-gated sodium channels and causing the nearby spot to support its action potential.The action potential can only move in one direction – from the cell body towards the axon terminal – because a spot of membrane that has just experienced one action potential is in a “refractory period” and cannot withstand another.