Which of the following best describes a consonant digraph?

A consonant digraph is defined as two consonant letters that combine to represent a single sound. This means that when the two consonants are placed together, they create a sound that is different from the individual sounds of each letter. For example, in the word "sh" as in "ship," the letters 's' and 'h' come together to make a unique sound that does not correspond to the sounds of 's' or 'h' alone.

The other options do not accurately reflect the definition of a consonant digraph. A group where each letter represents its own sound refers to single letters or combinations that maintain their individual phonetic sounds, which is not the case for digraphs. A group of sounds blended together could refer to blends or other phonetic combinations, but it does not specifically address the nature of digraphs as single sound representations. Lastly, a single vowel sound describes a single vowel letter or sound, which is unrelated to consonant digraphs that are focused on consonants.