This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2017, Subject name: Psychiatry
A 6 year old child who doesn't interact with other children of his age group and prefers playing alone in the same manner, is likely to be suffering from:- 
Select and explain. 
A. Autism, B. ADHD, C. Depression, D. Bipolar disorder
A: Autism
Answer: A: Autism 
Explanation: C/F of Autism (marked impairment in reciprocal social and interpersonal interaction): Absent social smile. Lack of eye-to-eye-contact. Lack of awareness of others' existence or feelings; treats people as furniture. Lack of attachment to parents and absence of separation anxiety. No or abnormal social play; prefers solitary games. Marked impairment in making friends. Lack of imitative behavior. Absence of fear in presence of danger