According to literacy concepts, which of the following represents a morpheme?

A morpheme is the smallest grammatical unit in a language that carries meaning. In this context, the suffix "-est" qualifies as a morpheme because it is a meaningful unit that is added to adjectives to indicate the superlative degree, such as in "tallest" or "fastest."

In contrast, alphabet letters, while essential to constructing words, do not have meaning on their own and do not qualify as morphemes. The /sh/ and /k/ sounds represent phonemes, which are the distinct units of sound in a language but do not convey meaning independently, making them distinct from morphemes. Thus, "-est" stands out as the only option that conveys meaning as a part of word construction.