All of the following are manners of articulation except:

The choice related to manners of articulation pertains to how speech sounds are produced and categorized based on the configurations of the vocal tract during articulation. Stops, nasals, and glides all describe different ways that airflow is manipulated to create distinct sounds.

Stops involve obstructing airflow completely before releasing it, creating a burst of sound (like the sounds [p], [t], and [k]). Nasals allow airflow to pass through the nasal cavity while the mouth is closed (as in [m] and [n]). Glides, like [w] and [j], are produced with less constriction than other consonants, allowing for a smooth transition from one sound to another.

On the other hand, monophthongs refer to a type of vowel sound characterized by a single, unchanging pitch during its articulation (such as [a], [e], [i], [o], and [u]). Since monophthongs describe a category of vowel sounds rather than a manner in which consonants are articulated, it does not fit within the definition of manners of articulation. This clearly distinguishes it from the other options, making it the correct choice.