A 15 year old boy feels that the dirt has hung onto him whenever he passes through the dirty street.This repetitive thought causes much distress and anxiety.He knows that three is actually no such thing after he has cleaned once but he is not satisfied and is compelled to think so.This has lead to social withdrawal.He spends much of his time thinking about the dirt and contamination.This has affected his studies also.The most likely diagnosis is:

• A. Agoraphobia
• B. Adjustment disorder
• C. Obsessive compulsive disorder
• D. Conduct disorder