question: Q:The study is performed to examine the association between type 2 diabetes mellitus (DM2) and Alzheimer's disease (AD). Group of 250 subjects diagnosed with DM2 and a matched group of 250 subjects without DM2 are enrolled. Each subject is monitored regularly over their lifetime for the development of symptoms of dementia or mild cognitive impairment. If symptoms are present, an autopsy is performed after the patient's death to confirm the diagnosis of AD. Which of the following is most correct regarding this study?? 
  {'A': 'It is a retrospective observational study.', 'B': 'It can provide proof of causation between DM2 and AD.', 'C': 'Relative risk cannot be determined from this study.', 'D': 'It is a prospective observational study.', 'E': 'It is a case-control study.'},