Question

a neural ______ or, chemical messenger, travels across the synapse and binds to a neural ______.
options:
transmitter...receptor
transmitter...transmitter
receptor...transmitter
receptor...receptor

Explanation:

In neural communication, a neural transmitter (chemical messenger) is released into the synapse and travels to bind with a neural receptor on the target neuron. The other options are illogical: a transmitter can't bind to another transmitter, a receptor isn't the chemical messenger that travels, and a receptor can't bind to another receptor in this context.

Answer:

A. transmitter...receptor