A 6-year-old substitutes [t] for /s/, [d] for /z/, [p] for /f/, and [b] for /v/. Intervention would target which linguistic level?

• A. Morphology
• B. Semantics
• C. Phonology
• D. Syntax

Answer: (C)

Phonology is being tested here—the study of how speech sounds are organized and produced. The child consistently substitutes s and z with t and d, and f and v with p and b, which are sound-level errors. That pattern points to a phonological issue, not to meaning, word forms, or sentence structure. Intervention would focus on producing and differentiating the target phonemes, and on adjusting the sound patterns used in speech. In contrast, morphology, semantics, and syntax deal with word forms, meaning, and grammar, not with how sounds are systematically produced. So the best linguistic level to target is phonology.