Which of the following examples are considered morphemes?

Morphemes are the smallest units of meaning in a language, and they can be classified as either free morphemes, which can stand alone as words, or bound morphemes, which must attach to other morphemes to convey meaning. In the context of the provided choices, the first option includes examples of both bound morphemes—“re” (as in redo), “un” (as in unhappy), “ing” (as in running), and “ed” (as in walked). Each of these prefixes or suffixes modifies the meaning of the base word they are attached to, which is a fundamental characteristic of morphemes.

The other options consist of larger linguistic units; for example, words (the second option) contain morphemes but are not themselves morphemes. Phrases and sentences are even larger constructs that convey meaning but are combinations of words. Similarly, nouns, verbs, adjectives, and adverbs (the third option) are parts of speech and thus larger units that can be made up of one or more morphemes. Lastly, subjects, predicates, objects, and complements (the fourth option) relate to sentence structure and do not represent individual units of meaning in the same way morphe