**Core Concept**
Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social communication and social interaction across multiple contexts, including deficits in nonverbal communicative behaviors used for social interaction, and deficits in developing, maintaining, and understanding relationships. Additionally, individuals with ASD often exhibit restricted, repetitive patterns of behavior, interests, or activities.

**Why the Correct Answer is Right**
The child's delayed speech onset and preference for routine are indicative of restricted interests and repetitive behaviors. Her difficulty with social interactions, such as playing with other children, and her tantrums related to changes, suggest deficits in social communication and interaction. These symptoms align with the diagnostic criteria for Autism Spectrum Disorder.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely unrelated to the child's symptoms, as it does not address the social communication and interaction deficits or the restricted interests and repetitive behaviors characteristic of ASD.

**Option B:** While ADHD shares some symptoms with ASD, such as difficulties with social interactions and repetitive behaviors, the primary features of ADHD are inattention, hyperactivity, and impulsivity, which are not mentioned in the scenario.

**Option C:** This option is a normal developmental stage, and the child's delayed speech onset and restricted interests suggest a more significant underlying issue than a simple developmental delay.

**Option D:** This option is not a specific diagnosis and does not address the child's symptoms of delayed speech onset, social interaction deficits, and restricted interests.

**Clinical Pearl / High-Yield Fact**
ASD is a spectrum disorder, meaning that individuals with ASD can exhibit a wide range of symptoms and severity levels. Early diagnosis and intervention are critical for improving outcomes and quality of life for individuals with ASD.

**Correct Answer:** C. Developmental delay.