Final answer:
Mr. Monk's repetitive thoughts about dirt and germs are an obsession, and his behavior of washing hands precisely three times each hour is a compulsion. The repeated thoughts are unwanted, causing distress, and the washing is performed as an attempt to alleviate this distress or prevent perceived negative outcomes.
Step-by-step explanation:
During the day, Mr. Monk has repetitive thoughts about dirt and germs, which reflect an obsession. To deal with these unpleasant images, he engages in the act of carefully washing and disinfecting his hands precisely three times each hour. This washing behavior reflects a compulsion. Therefore, the correct answer to the question would be 'b. an obsession; a compulsion'. Obsessions are characterized by persistent, unwanted thoughts or images that cause distress, while compulsions are repetitive behaviors that a person feels driven to perform in response to an obsession, often meant to reduce distress or prevent a feared event or situation.