Consider a study investigating the relationship between a new marketing strategy (X) and an increase in sales (Y). The study finds that:

When X is implemented, Y increases.

Variations in the intensity of X are systematically associated with variations in Y.

After controlling for external variables, the relationship between X and Y remains significant.

Given these findings, which degree of causality is most likely being demonstrated, and why?

a. Conditional causality because X is necessary but not sufficient on its own to increase Y; other factors are also required. b. Absolute causality because X is both necessary and sufficient to increase Y. c. Contributory causality because X is neither necessary nor sufficient to increase Y, but it still significantly contributes to the increase. d. None of the above because the evidence does not support any specific degree of causality.