Question

a neural __________ or, chemical messenger, travels across the synapse and binds to a neural __________.
o transmitter...receptor
o transmitter...transmitter
o receptor...transmitter
o receptor...receptor

Explanation:

Neural transmitters (chemical messengers) cross synapses. They bind to neural receptors (specific sites on neurons). Other options are incorrect as receptors don't act as transmitters and vice - versa in this context.

Answer:

A. transmitter...receptor