The introduction of a pleasant stimulus is to as the withdrawal of a pleasant stimulus is to

50% because no one is smart enough to relize that money makes the world go round and 99% of the earth hates donald trump the other 1% is the republicans go figure right

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.