Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The word "vital" is classified as an adjective because it describes or modifies a noun by expressing the quality or importance of the noun it accompanies. In English, adjectives are words that provide more information about a noun, often indicating characteristics such as size, color, shape, or significance. The term "vital" specifically relates to something that is essential, critical, or necessary for life or for the functioning of a system. For instance, in the phrases "vital signs" or "vital resources," "vital" indicates that the signs or resources are crucial and indispensable.

In contrast, a noun is a person, place, thing, or idea; an adverb typically modifies verbs, adjectives, or other adverbs and often answers questions like how, when, or where; and a verb represents an action, occurrence, or state of being. Since "vital" does not fulfill any of these roles, it is accurately identified as an adjective, making C) the correct answer. Understanding this classification enhances comprehension of how words function within sentences and facilitates more precise communication.