Curare blocks the action of acetylcholine by occupying its receptor sites.In this context,what is curare

A)  a neurotransmitter 
B)  an agonist 
C)  a neuromodulator 
D)  an antagonist

Acetylcholine

A neurotransmitter involved in many functions including muscle movement and memory.

Curare

A toxic plant extract used traditionally as an arrow poison and medically to relax muscles during surgery.

Antagonist

A substance that blocks or dampens the action of a neurotransmitter or hormone, or a character in a story who opposes the protagonist, creating conflict.