A nurse is caring for a child whose guardians report that the child is consistently unable to speak during class and other social situations. The nurse should identify that the child is experiencing which of the following anxiety disorders?

Selective mutism is an anxiety disorder characterized by a child's consistent inability to speak in specific social situations — most commonly school or other public settings — despite speaking normally in familiar environments such as at home. The key diagnostic feature is that the child can speak but does not, specifically in contexts where speaking is socially expected, and this pattern persists for more than one month. The stem describes exactly this pattern: the child cannot speak during class and other social situations, which is the hallmark presentation of selective mutism. Generalized anxiety disorder involves excessive, difficult-to-control worry about many different topics and does not specifically manifest as an inability to speak. Agoraphobia involves fear and avoidance of situations where escape might be difficult, such as crowds or public transportation, without the specific characteristic of speech absence. Separation anxiety disorder involves excessive fear of separation from attachment figures, which may produce school avoidance but is not defined by the inability to speak in social settings. The selectivity of the mutism — only in social situations while speech is preserved in comfortable settings — is the defining clinical clue that identifies selective mutism.