单项选择题
A．Risk factors in heart attacks. B．Seasonal and temporal patterns of heart attacks. C．Cardiology in the 1980s. D．Diet and stress as factors in heart attacks.
A．We now fully understand how risk factors trigger heart attacks. B．We recently began to study how risk factors trigger heart attacks. C．We have not identified many risk factors associated with heart attacks. D．We do not fully understand how risk factors trigger heart attacks.
A．High in cholesterol. B．Conjugal affection. C．Eating fatty foods. D．Being under stress.