On September 12, 2001, psychologists Jennifer Talarico and David Rubin had university students complete questionnaires about how they learned about the terrorist attacks against the United States on the previous day. For comparison, students also described some ordinary event that had occurred in their lives at about the same time, such as going to a sporting event. Over the next year, students were periodically asked to again describe their memories of the 9/11 attacks and of the ordinary event. The results indicated that: a. the flashbulb memories, but not the everyday memories, were preserved virtually unchanged over time. b. both flashbulb memories and everyday memories improved over time. c. both the flashbulb memories and the everyday memories decayed over time. d. the everyday memories, but not the flashbulb memories, were preserved virtually unchanged over time.