A pronoun must agree with its antecedent in number (singular or plural) and gender (masculine or feminine).
In this sentence, Harold is the antecedent of his, he'd, and his.
In the following sentence, Garcias is the antecedent of they, even though it follows the pronoun.
Look at the next example. Here, Peterson and Mancini is a compound antecedent, which requires the plural pronoun their.
Agreement problems with indefinite pronouns
Indefinite pronouns cause many agreement problems. Some pronouns (several, few, both, and many) are clearly plural and take both plural verbs and plural pronouns.
Some pronouns may “feel” plural, but are singular and take singular verbs and pronouns. In this group are each, either, neither, everyone, everybody, no one, nobody, anyone, anybody, someone, and somebody.
When the use of a singular form would lead to a statement that doesn't make sense, you should use a plural form. For example, in the sentence Everyone left the lecture because he thought it was boring, they would be a better choice than he for the pronoun. However, the general rule is to use singular forms of verbs and pronouns with these indefinite pronouns.
Some indefinite pronouns (none, any, some, all, most) fall into an “either/or” category; and they may take singular or plural verbs and pronouns, depending on meaning. Sometimes the distinction is subtle.
If a plural meaning is not clear from the context, use singular verbs and pronouns.
Pronouns with collective nouns
Collective nouns can also require either singular or plural verbs and singular or plural pronouns, depending on meaning.
However, if you are uncertain, choose a singular verb and a singular pronoun, or rewrite the sentence to make it clearly plural.
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