True aboutAutism -a) Persistent delusionb) Persistent hallucinationc) Incoordinate social interactiond) Defective reciprocal interactione) Onset after 5 yr

**Core Concept**
Autism, also known as Autism Spectrum Disorder (ASD), is a neurodevelopmental disorder characterized by impaired social interaction, verbal and nonverbal communication, and repetitive behaviors. The clinical presentation of autism is diverse, and individuals with autism may exhibit varying degrees of impairment in these areas.

**Why the Correct Answer is Right**
The correct answer, **d) Defective reciprocal interaction**, accurately describes a core feature of autism. Individuals with autism often struggle with initiating and maintaining reciprocal social interactions, such as conversations or play. This is due to difficulties with understanding social cues, developing and maintaining relationships, and adapting to changing social situations. The defective reciprocal interaction in autism is thought to result from abnormalities in brain regions involved in social cognition, including the amygdala, fusiform gyrus, and superior temporal sulcus.

**Why Each Wrong Option is Incorrect**
**Option A:** **Persistent delusion** is a characteristic of psychotic disorders, such as schizophrenia, and is not a feature of autism.
**Option B:** **Persistent hallucination** is also a feature of psychotic disorders and is not a defining characteristic of autism.
**Option E:** **Onset after 5 yr** is incorrect because autism is a developmental disorder that typically becomes apparent in early childhood, often before the age of 5.

**Clinical Pearl / High-Yield Fact**
Autism is a spectrum disorder, meaning that individuals with autism can exhibit a wide range of symptoms and severity of impairment. The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria for autism emphasize the importance of social communication and interaction difficulties, as well as repetitive behaviors, in the diagnosis of autism.

**Correct Answer: D. Defective reciprocal interaction.**