<prompt> Which one of the following statements about influence of smoking on risk of coronary hea disease CHD is not true?Influence of smoking is independent of the risk factors for CHDInfluence of smoking is only additive to other factors for CHDInfluence of smoking is synergistic to other risk factors for CHDInfluence of smoking is directly related to number of cigarettes smoke per day  <response>: There is evidence that influence smoking not only independent of but also synergistic with other risk factors such as hypeension and elevated serum cholesterol. This means that the effect are more than additive. Ref-Park;s textbook of Preventive and Social Medicine 24th edition. 