What is the role of phonetic value in digraphs?

The correct choice highlights that the role of phonetic value in digraphs is to assign a single sound to a pair of letters. In phonetics, a digraph consists of two letters that together produce one sound. For example, in the word "shoes," the combination of the letters 's' and 'h' forms the single sound /ʃ/. This is an essential element of phonics instruction, as learning about digraphs helps students improve their decoding skills, allowing them to read more fluently.

When students understand that specific pairs of letters create a distinct sound, it helps them to recognize these patterns in various words, enhancing their overall reading ability. This knowledge supports them in sounding out unfamiliar words by applying their understanding of letter combinations, a crucial part of early literacy development.

The other choices do not accurately describe the function of phonetic value in digraphs, as they relate to different aspects of language and grammar rather than the sound-for-letter correspondence that digraphs represent.