In a particular community, several high school students were diagnosed with diabetes mellitus Type 2 ...

In a particular community, several high school students were diagnosed with diabetes mellitus Type 2 during the annual high school health fair.
 
  Over the next few years, the nursing staff developed and implemented educational programs about the risk factors for diabetes mellitus Type 2 and proper nutrition. Which of the following would be most useful for the nurses to use to determine if they are having any impact?
  a. The epidemic of diabetes in the high school is gradually ending.
  b. The incidence of diabetes is slowly decreasing during screening events.
  c. The prevalence of diabetes is slowly decreasing during screening events.
  d. The risk for diabetes is slowly increasing over time.