Which is a symptom of obsessive-compulsive disorder?

All of the listed symptoms—excessive hand washing, ritualistic behaviors, and intrusive thoughts—are key characteristics of obsessive-compulsive disorder (OCD). Individuals with OCD often experience obsessions, which are unwanted and intrusive thoughts that cause significant anxiety or distress. To mitigate this anxiety, they may engage in compulsions, which are repetitive behaviors or mental acts driven by these obsessions.

Excessive hand washing is a common compulsion, particularly among those whose obsessions are centered around cleanliness or contamination fears. Ritualistic behaviors refer to a variety of repetitive actions that individuals feel compelled to perform in a specific manner, often to prevent a feared outcome associated with their obsessions. Finally, intrusive thoughts are a hallmark of OCD, as these thoughts will frequently disrupt a person's daily life, leading to distress and the need to engage in compulsions as a coping mechanism.

Thus, the correct choice encompasses the full range of symptoms commonly associated with OCD, highlighting the disorder's complex interplay between obsessive thoughts and compulsive actions.