Final answer:
The subject of this question is 'Graphemics', which refers to the study of writing systems and the relationship between written symbols and sounds. Therefore, the correct option is B) Graphemics.
Step-by-step explanation:
The subject of this question is Graphemics. Graphemics refers to the study of writing systems and the relationship between written symbols and the sounds they represent. In this case, the question is about the knowledge of letter blends and digraphs, which are part of graphemics.