Answer: C

Reasoning: In a retained infantile swallow the entire infantile neuromuscular swallowing pattern persists; the lips and perioral muscles contract strongly and the tongue thrusts forward with no posterior occlusal support, making re-education of the habit and long-term stability of orthodontic correction very difficult. Simple tongue thrust (seen transiently during the mixed dentition) usually resolves once the anterior teeth erupt, and complex tongue thrust has a guarded but better response to myofunctional or appliance therapy. Therefore the retained infantile swallow carries the poorest prognosis for treatment and relapse control [Shah et al., 2021 PMID 34413610; Wildman, 1976 PMID 1067201].