Which structural factor has the most adverse effect on articulation?

Class III malocclusion has the most adverse effect on articulation primarily due to its impact on the alignment and occlusion of the teeth and jaws. In Class III malocclusion, the lower jaw is positioned more forward than the upper jaw, which can lead to significant challenges in how sounds are produced. This misalignment can affect the tongue's ability to properly articulate certain sounds, especially those that require precise positioning of the tongue against the teeth or the roof of the mouth, such as sibilants like "s" and "z."

Anomalies in tooth alignment also influence airflow and resonance, which are critical for clear speech. Individuals with Class III malocclusion may experience difficulty in producing specific phonemes accurately, leading to speech that may be perceived as less intelligible. This articulatory challenge is a major reason why this structural factor is considered to have a particularly adverse effect on articulation compared to the other options provided.