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: Psychiatry
A 12-year-old boy is brought to your clinic for being very strange in his behaviours. He is late to school because he has to be in the shower for more than 2 hours. He feels compelled to use the soap repeatedly to clean off the 'germs' which he is worried off. He feels compelled to do this although he thinks that it is senseless. He checks his bag for his pen every 5 minutes. He has always struggled to complete his exams in time. Which of the following is the MOST likely diagnosis? 
Select and explain. 
A. Specific phobia for germs, B. Autism Spectrum Disorder, C. Obsessive Compulsive Disorder, D. Cyclothymia
C: Obsessive Compulsive Disorder
Answer: C: Obsessive Compulsive Disorder 
Explanation: Obsessive Compulsive Disorder is associated with intrusive thoughts (obsessions) and unusual rituals and activities (compulsions). It is recognised by the patient as senseless. In this scenario, repeated thoughts of germs is obsession and repeated cleaning and checking for pen in his bag is compulsion. Majority of the cases of OCD begin in adolescence. Specific phobia for germs: will not have compulsions or obsessions. It will lead to avoidance of contaminated objects. Ref: Kaplan & Sadock's Synopsis of Psychiatry, By Benjamin J Sadock, M.D., Harold I. Kaplan, Virginia A Sadock, M.D, 10th Edition, Page : 1271