This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Behavioral Disorders in Children, Subject name: Pediatrics
A 3 years old boy with normal developmental milestones with delayed speech, has difficulty in communication and concentration. He is not making friends. Most probable diagnosis is: 
Select and explain. 
A. Autism, B. ADHD, C. Mental retardation, D. Specific learning disability
A: Autism
Answer: A: Autism 
Explanation: The given scenario where child is having delayed speech and difficulty in communication and concentration and is not making friends, suggests - Autistic spectrum disorder. Autistic disorder: qualitative impairment of social behaviour impairment of communication skills stereotypic & restricted behaviour onset before 3 years. More common in boys