According to Campbell, Why Is Regression to the Mean Such

Multiple Choice

According to Campbell, why is regression to the mean such a likely explanation when evaluating the effects of social programs (e.g., speeding crackdowns) ?

A) programs to fix some problem are usually begun after an especially bad year
B) program evaluation is always correlational rather than experimental
C) it is usually easy to rule out all other confounds
D) regression is the one confound that cannot be evaluated by comparison with a control group