Answer:
Obsession; compulsion
Step-by-step explanation:
Obsession: The term obsession is defined as a mental illness or disorder in which an individual experience repeated and unwanted feelings, images, thoughts, or sensations.
Compulsion: The term compulsion is defined as rule-based behavior that an individual should perform a specific task to make oneself feel better and normal and avoid negative consequences.
In the question above, Kate's thoughts beat illustrate a(n) obsession, and Charlie's behavior best illustrates a(n) compulsion.