Which of the following is an example of a grapheme?

The choice "Ch" is considered a grapheme because it represents a specific letter or group of letters that correspond to a single sound in spoken language. Graphemes are the smallest unit in a writing system that represents phonemes, or sounds, in a language. In this case, "Ch" is a digraph, which is a type of grapheme made up of two letters that together create one sound, such as in the words "chocolate" or "chair."

Graphemes can consist of single letters, combinations of letters, or even entire characters in non-alphabetic writing systems. The other options provided do not fit the definition of a grapheme: a vowel sound refers to a specific type of phoneme and does not represent written language on its own; a phoneme is the basic unit of sound in oral language, not writing; and a word is a combination of letters or sounds that convey meaning but is larger than a single grapheme. Thus, "Ch" specifically serves as an example of how letters are utilized in phonetic representation within words, making it the correct answer.