Final answer:
The section of a voiceless stop consonant characterized by complete airflow obstruction and no sound is the closure (stop gap) phase (b). The closure physically stops airflow and acoustically is silent, differentiating it from other sections like aspiration, transient release, frication, and VOT duration.
Step-by-step explanation:
With regard to the production of voiceless stop consonants, during the closure (stop gap) phase, there is a complete obstruction of airflow through the vocal tract. This period is physically marked by the stoppage of air, which is necessary to build up pressure behind the point of closure.
Acoustically, this period is characterized by silence, as no sound is transmitted through the air since the airflow is entirely blocked.
Therefore, the answer to the student’s question is (b) closure (stop gap), which reflects the phase in vocalization when there is a complete obstruction of airflow and, consequently, no sound. Other sections such as aspiration, transient release, frication, and the whole Voice Onset Time (VOT) duration involve different features of speech sound production.
Aspiration includes a burst of air following the release of a closure, transient release is the brief moment of release between the closure and the onset of vocal cord vibration, frication is associated with turbulent airflow, and VOT is the entire duration from the release of closure to the onset of vocalization.