This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
3 year old girl having delayed milestones, playing with
herself, difficulty in learning is likely to be suffering from 
Select and explain. 
A. Mental retardation, B. Autism, C. Specific Learning Disorder, D. ADHD
B: Autism
Answer: B: Autism 
Explanation: None