Final answer:
The two consonant groupings -tch and -dge are known as 'digraphs,' which are pairs of letters representing a single sound. The correct option is B.
Step-by-step explanation:
The correct answer to the question is B) Digraphs. A digraph is a pair of letters that together represent one sound, as in the long e spelled by various digraphs like , , – and in the case of the question, the <-tch> and <-dge> sounds.
Trigraphs involve three letters to represent one sound, which is not applicable in this case, therefore option C is incorrect.
Option A, blends, is also incorrect because blends involve two or more consonants which each maintain their individual sounds when combined, unlike a digraph which represents just one. Lastly, option D, 'None of the above,' does not apply since digraphs are a confirmed linguistic concept that fits the description. The correct option is B.