**Core Concept**
The question describes a 16-year-old boy with persistent delusions of being mocked by classmates and a strong fear of social situations, including going out of the market. This pattern reflects **positive symptoms of psychosis**, particularly **delusions of persecution** and **social anxiety**, which are hallmark features of schizophrenia in adolescence.

**Why the Correct Answer is Right**
Schizophrenia in adolescents often presents with **delusions of persecution**, **paranoid ideation**, and **aversion to social interaction**. The boy’s belief that classmates laugh at him and talk about him is a classic example of **delusional thinking**. His fear of being harmed or ridiculed is not merely anxiety but reflects a **distorted reality perception**, which is central to schizophrenia. Unlike anxiety disorders, these symptoms persist despite reality testing and are not proportional to situational stress. The presence of both delusions and social withdrawal strongly supports a psychotic disorder like schizophrenia.

**Why Each Wrong Option is Incorrect**
Option A: Anxiety disorder involves excessive worry or fear but not delusions. The boy’s belief that others are mocking him is not a fear of future events but a fixed, false belief, which is not consistent with pure anxiety.
Option B: Manic-depressive psychosis (bipolar disorder) involves mood swings, manic or depressive episodes, and often grandiosity or irritability. There is no evidence of mood lability or euphoria here.
Option C: Adjustment reaction is a temporary response to stress, typically resolving within weeks. The boy’s symptoms are chronic and delusional, not a short-term stress response.

**Clinical Pearl / High-Yield Fact**
In adolescents, **delusions of persecution** and **avoidance of social settings** are red flags for schizophrenia, especially if they persist beyond 6 months. Early recognition is crucial for effective treatment and prevention of deterioration.

✓ Correct Answer: D. Schizophrenia