The morphophonemic process that makes the plural ending of words like pictures, frames, malls, and clothes pronounced as [z] is called:

• A. Insertion
• B. Deletion
• C. Assimilation
• D. Substitution

Answer: (C)

Assimilation is at work here, specifically voicing assimilation of the plural suffix. In English, the plural ending -s is realized as different sounds (like [s], [z], or [ɪz]) depending on the surrounding sounds. When the stem ends with a voiced segment, the voicing spreads to the plural suffix, so the ending is produced as [z]. That’s why words like pictures, frames, malls, and clothes commonly sound with a [z] at the end—the voiced quality of the preceding sound colors the plural ending. It’s not about adding or deleting sounds or substituting one sound for another; it’s about the plural suffix taking on the voicing of the neighboring sound to ease articulation.