Which suffix expresses plurality or possession when added to a noun, among other grammatical functions?

The answer is correct because an inflectional suffix is specifically designed to modify a word to express grammatical relationships such as plurality and possession. When added to a noun, inflectional suffixes like “-s” or “-es” create plural forms (e.g., "cat" becomes "cats"), while the possessive form typically uses “-’s” (e.g., "dog" becomes "dog's").

Inflectional suffixes differ from derivational suffixes, which change a word's meaning or its part of speech but do not directly convey grammatical functions like showing plurality or possession. Affixes is a broader term that includes both derivational and inflectional suffixes but does not specifically refer to the grammatical changes associated with nouns. The concept of a compound suffix does not apply here, as it usually refers to a combination of two or more morphemes that may not specifically address plurality or possession.