Final answer:
The correct possessive pronoun to use is 'its' because 'union' is a singular collective noun that refers to the group acting as a unified entity. Thus, it requires a singular possessive pronoun.
Step-by-step explanation:
The correct answer to your question is "The union officially voiced its opposition to the management's proposal." The word "its" is used because the word "union" is a collective noun, which is singular and thus requires a singular possessive pronoun. In English grammar, collective nouns refer to a group of individuals or things as a single entity, and when that entity is acting as a single unit, it takes a singular pronoun for agreement. Even though a union comprises many members, the entity itself is treated as one when the group acts with a unified position, as opposed to the individual actions or opinions of its members. However, it’s worth noting that in British English, collective nouns can take either singular or plural pronouns depending on whether the action refers to the group acting as a whole or its members acting individually. Since the sentence implies the union is acting with one voice in opposition, the correctly matched pronoun is singular.