Typically, people who have diets high in saturated fat have an increased risk of heart disease. Those who replace saturated fat in their diets with unsaturated fat decrease their risk of heart disease. Ttherefore, people who eat a lot of saturated fat can lower their risk of heart disease by increasing their intake of unsaturated fat. Which one of the following, if assumed, most helps to justify the reasoning above? ['People who add unsaturated fat to their diets will eat less food that is high in saturated fat.', 'It is difficult to move from a diet that is high in saturated fat to a diet that includes very little fat.', 'Adding unsaturated fat to a diet brings health benefits other than a reduced risk of heart disease.', 'Taking steps to prevent heart disease is one of the most effective ways of increasing life expectancy.']