Answer:
D. neither
Explanation:
The following indefinite pronouns are always singular: ... one, someone; anybody, everybody, nobody, somebody; another, the other; either, neither ... [singular idea, since all is referring to cake]; All of the cupcakes are gone.
Indefinite pronouns are non-specific words like someone, others, several or none. Some of these pronouns are always singular or always plural. ... -body, -one and -thing, along with the words one, another, each, either, neither and much.
