Answer:
b. a flashbulb memory.
Step-by-step explanation:
A flashbulb memory is a memory which is a vivid and detailed description of the moment in which any emotional news would hear in the past. These memories are a product of the arousal of emotion, and surprise. It can be both positive and negative memory. In the given case, the memory that Casey witnesses are a negative one. Such memories are more detailed. They are very unpleasant and because of these memories, the person wants to avoid to relive them anytime.