What type of suffix denotes the act of, state of, or quality of a noun?

The choice indicating noun suffixes is correct because these suffixes are used to create nouns that refer specifically to the act of, state of, or quality of something. For example, the suffix "-tion" in "celebration" denotes the act of celebrating, while "-ness" in "kindness" refers to the quality of being kind. These suffixes help convey a specific meaning related to actions, states, or qualities that are intrinsic to the noun they modify.

Other types of suffixes serve different grammatical purposes: adjectival suffixes typically create adjectives that describe nouns, verb suffixes form verbs that indicate actions or states, and pronoun suffixes relate to pronouns, which replace nouns. Thus, noun suffixes are uniquely positioned to create words that embody the concept of an act, state, or quality, making them the correct answer for this question.