In her study of married people, Aiko finds an association between more frequent religious service participation and staying married longer. She also explores whether stronger community ties explain at least part of this association. For this example, which of the following scenarios is MOST illustrative of using a control variable in regression analysis?
a. testing whether community ties predicts religious participation for both married and unmarried people
b. testing whether the association between religious participation and marital stability is evident when looking separately at higher and lower religious participation groups
c. testing whether controlling for community ties reduces the association between religious participation and marital stability
d. testing whether religious participation predicts community ties for both married and unmarried people