Final answer:
Autistic disorder is best defined as a pervasive developmental disorder characterized by difficulties with social interaction and communication. It is also known as Autism Spectrum Disorder (ASD), with symptoms varying in severity from person to person.
Step-by-step explanation:
The best definition for autistic disorder among the provided options is: B) A pervasive developmental disorder characterized by difficulties with social interaction and communication. Autism Spectrum Disorder (ASD) is a neurodevelopmental condition marked by challenges in social interaction, communication abilities, and often includes repetitive behaviors and fixed interests. The symptoms and their severity vary greatly across individuals with ASD. More formally known as Autism Spectrum Disorders, ASD is one of the fastest-growing developmental disorders. Children with autism might struggle with eye contact, reading social cues, or feeling empathy. Although the disorder is more common in males than females, it is a wide spectrum where some individuals may possess good-to-excellent language skills and do not view their condition as a disability but as a different way of processing information.