A researcher has found that the more time athletes spend training in track and field, the lower their times in the 100-meter run. She determines that this result means that training causes drops in times. Which of the following is true about this study?

a. The researcher has conducted a longitudinal study.
b. The researcher has conducted a survey.
c. The researcher has conducted a study that resulted in an illusory correlation.
d. The researcher has falsely determined that correlation proves causation.

e. The researcher has conducted a correlational study that resulted in a positive correlation.