A multiple-regression analysis is run to examine third variables as a follow-up to the study indicating that boys with unusual names are more likely to commit crimes. Unusual names, ethnic backgrounds, and geographical regions are all included as predictor variables. Even after controlling for all these variables, unusual names still predict criminal activity. Which of the following explains why this study doesn't establish causation?

A. Temporal precedence isn't established between the variables.
B. The beta values are not shown, so there isn't enough information to establish covariance.
C. There may be some other third variable.
D. No significant cross-lag correlations were found.