In such cases, the masculine pronoun “to be” was traditionally used in language and writing: everyone has their own opinion. Some collective nouns are usually used with a singular verb (the bourgeoisie, the proletariat). Other collective nouns are usually used with plural verblage (police, militia, clergy). The construction is one of those that create confusion when it comes to the subject-verb agreement in the relative sentence. Decide if one or that is the precursor of whom in choosing the right verb. .