**Core Concept**
Autism, also known as Autism Spectrum Disorder (ASD), is a neurodevelopmental disorder characterized by impairments in social interaction, verbal and nonverbal communication, and repetitive behaviors. The underlying pathophysiology involves abnormalities in brain structure and function, particularly in regions responsible for social cognition and communication.

**Why the Correct Answer is Right**
The core features of autism are deficits in social communication, social interaction, and restricted/repetitive patterns of behavior, interests, or activities. This is often accompanied by delays in language development, difficulties with eye contact, and challenges with understanding and interpreting social cues. The social communication difficulties can manifest as problems with initiating or maintaining conversations, understanding nonverbal cues, and developing and maintaining relationships. The restricted/repetitive behaviors can include hand flapping, body rocking, and insistence on sameness.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the core characteristics of autism. While sensory processing issues can be present in individuals with autism, they are not a defining feature of the disorder.

**Option B:** This option is incorrect because attention deficit hyperactivity disorder (ADHD) is a separate neurodevelopmental disorder characterized by symptoms of inattention, hyperactivity, and impulsivity.

**Option C:** This option is incorrect because intellectual disability (formerly known as mental retardation) is a separate diagnosis that involves significant limitations in intellectual functioning and adaptive behavior.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that autism is a spectrum disorder, and individuals with autism can exhibit a wide range of symptoms and severity. A diagnosis of autism is based on a comprehensive evaluation of an individual's behavior, communication, and development.

**Correct Answer:** D.