Which sounds require that the velopharyngeal port remains open?

The correct response highlights nasal sounds, which are characterized by the vibration of air through the nasal cavity. For nasal sounds, the velopharyngeal port must remain open to allow airflow to pass through the nose. This is essential for producing sounds like /m/, /n/, and /ŋ/ (as in "sing"). When the velopharyngeal port is open, it creates a connection between the oral cavity and the nasal cavity, enabling the distinct quality associated with nasal phonation.

In contrast, other sound categories do not require this airflow through the nasal cavity. For instance, vocal sounds can be produced without an open velopharyngeal port, as they primarily rely on vibrations of the vocal folds without needing nasal resonance. Frontal and back sounds also have specific articulatory placements and do not demand an open velopharyngeal port for proper production, focusing instead on oral airflow. Thus, nasal sounds are unique in this aspect, necessitating the open velopharyngeal port for their proper articulation.