Final answer:
The correct diagnosis for the student exhibiting symptoms such as auditory hallucinations, delusional thinking, and a flattened affect is schizophrenia, fitting the symptoms described in the DSM for this mental disorder.
Step-by-step explanation:
The student described in the question exhibits a decline in grades, social withdrawal, flattened affect, lack of motivation, auditory hallucinations, and delusional thinking. These symptoms align most closely with a diagnosis of schizophrenia, which is characterized by an inability to differentiate between reality and imagination, auditory hallucinations, delusions, flattened affect, and social withdrawal. This mental illness affects cognitive and emotional functioning, making it difficult for individuals to manage daily tasks and social interactions. Schizophrenia commonly develops in late adolescence or early adulthood and requires treatment with antipsychotic medications to manage symptoms. The correct diagnosis for the student mentioned in the scenario is c) Schizophrenia.