An investigator determines that "variable Z" is an effect modifier on the effect of smoking on risk of cardiovascular disease. Which of the following is the appropriate? A. Report the crude (unadjusted) risk ratio when describing the association between smoking and risk of cardiovascular disease. B. Report the adjusted risk ratio (adjusting for variable Z) when describing the association between smoking and risk of cardiovascular disease. C. Stratify the results by variable Z when reporting the risk ratio describing the association between smoking and risk of cardiovascular disease. D. None of the above