The answer is the smallest component of speech that carries meaning.
This option is incorrect. While morphemes are part of the language system, they are not arbitrary signals. They have specific meanings and functions within the language.
This option is incorrect. A phrase is a group of words that functions as a unit within a sentence, whereas a morpheme is much smaller, often just a single word or part of a word.
This option is incorrect. An individual speech sound is known as a phoneme, not a morpheme. Phonemes are the smallest units of sound in a language, but they do not carry meaning by themselves.
This option is correct. A morpheme is the smallest grammatical unit in a language that carries meaning. Examples include prefixes, suffixes, and root words. For instance, in the word "unhappiness," "un-", "happy," and "-ness" are all morphemes.