What is the smallest unit of speech sound classified as a phoneme?

The smallest unit of speech sound classified as a phoneme is represented by the phonetic symbol /k/. Phonemes are the distinct units of sound that can differentiate meaning in a language. For example, the phoneme /k/ can be found in words such as "cat" and "kite," where it plays a crucial role in distinguishing these words from others that have different sounds.

In contrast, a written letter refers to a character in the alphabet, which does not necessarily represent an individual sound in all cases. A syllable is a larger unit of sound that typically consists of a vowel sound and any accompanying consonants, making it larger than a phoneme. Lastly, a morpheme is the smallest grammatical unit in a language, which can be a word or a part of a word (like a prefix or suffix) carrying meaning, rather than specifically a sound unit. Thus, /k/ accurately represents the smallest unit of sound that can differentiate meaning in language, confirming it as the correct response.