Which of the following describes a developmental disability that affects social interaction and communication, typically emerging in early childhood?

The correct answer is autism, as it specifically refers to a developmental disability characterized by challenges in social interaction and communication. Autism Spectrum Disorder (ASD) usually becomes apparent in early childhood, with individuals often showing signs such as difficulties in understanding social cues, forming relationships, and engaging in conversation. This condition affects the brain's development, leading to various symptoms that can vary widely in severity.

Attention Deficit Hyperactivity Disorder (ADHD) primarily involves issues with attention, hyperactivity, and impulsivity, which can impact social functioning but do not fundamentally affect communication in the same way as autism. Down Syndrome, a genetic condition resulting from an extra chromosome, includes a spectrum of physical and cognitive challenges but is not specifically defined by social interaction issues. Cerebral Palsy is related to motor function impairments stemming from brain damage and doesn't inherently include communication deficits like those found in autism. Thus, autism is uniquely characterized by its impact on social interaction and communication from an early age.