Final answer:
Intervention for the child's language problem would target phonology. Phonology is the study of speech sounds and how they are used in a language. Targeting language intervention at the level of phonology can help the child learn to produce the correct sounds and improve their overall speech clarity.
Step-by-step explanation:
Intervention for the child's language problem would target phonology. Phonology is the study of speech sounds and how they are used in a language. The child's difficulty in producing certain sounds, such as substituting [t] for /s/, [d] for /z/, [p] for /f/, and [b] for /v/, indicates a phonological issue. Targeting language intervention at the level of phonology can help the child learn to produce the correct sounds and improve their overall speech clarity.