Explanation

The noun 'girl' is classified as a common noun because it refers to a general category of a person rather than a specific individual or entity. Common nouns are words that name general items, people, or concepts that are not unique. For instance, 'girl' can describe any female child or young adult, regardless of identity or context. In contrast, proper nouns name specific people, places, or organizations and are always capitalized; examples include 'Emily,' 'Paris,' or 'Nike'.

The other options, such as collective nouns, refer to groups of people or things, like 'team' or 'flock', and material nouns denote substances or materials, such as 'water' or 'gold'. Since 'girl' does not imply a collection or a specific substance but rather signifies any female in a general sense, it fits the definition of a common noun perfectly. Understanding this distinction is crucial for grasping how nouns function in language and helps in categorizing them accurately.