A study was conducted on 200 random Kalamazoo residents who previously and recently tested positive for COVID-19. The participants who tested positive were asked to describe all the people they interacted with and places they had been for the past week. The study aimed to identify the potential virus 'hotspots' in the city. What type of study does this describe? Question 17 options: A) Clinical Trial B) Unable to determine C) Randomized Controlled Experiment D) Retrospective Study E) Prospective Study