Gretchen is watching an action movie on television that involves an archaeologist who hunts for lost artifacts. In one scene he is running through a jungle while being chased by local residents who use blow guns to fire darts at him. He does not know that they have used curare on these darts, which is a very poisonous acetylcholine _______.
a. antagonist.
b. agonist.
c. sodium ion.
d. protein ion.