Problem: Which of the following is NOT a method that can be used to help reduce confounding in case-control studies? O A. Selecting cases about the same age as the controls. • B. Selecting cases who are the same race and ethnicity as the controls. • C. Collection of information on many variables that are associated with the condition of interest. O D. All of the above are methods that can be helpful to reduce confounding. O E. None of the above are methods that can be helpful to reduce confounding.