Which of the following is an example of an unvoiced consonant?

The selection of an unvoiced consonant from the given options highlights the characteristics of speech sounds that are produced without vibration of the vocal cords. Unvoiced consonants are articulated with more airflow and no accompanying vocal fold vibration.

In the case of your choice, the sounds /s/, /f/, and /th/ are indeed all unvoiced consonants. This means when pronouncing these sounds, the vocal cords do not engage. For instance, /s/ is produced by forcing air through a narrow channel in the vocal tract, and /f/ is produced similarly but with the upper teeth and lower lip. The /th/ sound, as in "think," is also unvoiced; it requires the tongue to be placed between the teeth while air flows past without vibrating the vocal cords.

Other options contain voiced consonants or combinations of voiced and unvoiced sounds. The presence of voiced consonants like /z/, /m/, /l/, /r/, and /g/ in the other choices makes them incorrect examples of entirely unvoiced consonants. Thus, the specific selection of /s/, /f/, and /th/ correctly highlights the category of unvoiced consonants.