Final answer:
Indefinite pronouns that can be sometimes singular and sometimes plural include everyone, somebody, nobody, anyone, and anything.
Step-by-step explanation:
An indefinite pronoun is a pronoun that does not refer to a specific person, place, or thing. Some indefinite pronouns can be both singular and plural depending on the context. Examples of such pronouns are: everyone, everybody, everything, someone, somebody, something, no one, nobody, nothing, anyone, anybody, and anything.
For example, 'Everyone is here' (singular verb) and 'Everyone have their own opinions' (plural verb).
Similarly, 'Nobody believes in him' (singular verb) and 'Nobody have shown their interest' (plural verb).