Which of the following sounds is an example of a glide?

A glide is a type of consonant sound that features a transition in the articulatory position, resembling a vowel more than a consonant. The sound 'w' is produced with the articulators transitioning from a more rounded position to a more open position, which is characteristic of how glides function in language.

Glides, such as 'w' and 'y', smooth the transition between vowel sounds and serve to blend the two sounds together, often occurring at the beginning of syllables. The 'w' sound leads into the following vowel and has a dynamic quality that contributes to the fluidity of speech.

In contrast, the other options represent different types of sounds. The sounds 'm' and 's' are considered nasal and sibilant sounds, respectively, while 'k' is a stop consonant. None of these sounds exhibit the glide characteristics that 'w' does, which is why 'w' is the correct example of a glide from the provided options.