3.One thousand randomly chosen men between the ages of 45 and 60 were interviewed with regard to their smoking, drinking and other habits as well as the presence or absence of heart disease and bronchitis. Those men reporting symptoms consistent with heart disease were 50 per cent more likely to be smokers than men not reporting those symptoms. The association between heart disease and smoking persisted after controlling for other potential risk factors for heart disease. (From Maxcy

-Rosenau, 17th ed.)

A.Cross-sectional

B.Case control

C.None of these options

D.Cohort