GRC often rely heavily on raising money for an annual fund to support operations. Alumni are typically solicited for donations to the annual fund. Studies suggest that the graduate's annual income is a good predictor of the amount of money he or she would be willing to donate, and there is a reasonably strong, positive, linear relationship between these variables. In the studies described:
a. annual income is the predictor variable
b. the correlation between annual income and the size of the donation is negative.
c. the size of the donation to the annual fund is the predictor variable
d. All of the above
None of the above