What are the smallest units of meaning in a language that can stand alone or have prefixes/suffixes?

The correct answer is morphemes, as they are the smallest units of meaning in a language. Morphemes can be whole words like "cat" or "book," but they can also be parts of words, such as prefixes or suffixes that modify the meaning of a base word, like "un-" in "undo" or "-s" in "cats." This capacity to both exist independently as stand-alone words and also attach to other elements of language highlights their fundamental role in constructing meaning.

Words, while accurate to a degree, are broader units of meaning that may consist of one or more morphemes. Phrases consist of multiple words structured together to convey a complete idea, but they do not represent the minimal meaningful units. Clauses are made up of phrases and express a complete thought or idea, often containing a subject and a verb, but they also consist of multiple words and therefore are larger than the smallest units of meaning. Thus, morphemes are the most appropriate answer as they encapsulate the essence of individual meaning within the structure of language.