The higher the average cholesterol intake among the residents of a nation, the higher the incidence of heart disease in that nation; the lower the average cholesterol intake, the lower the incidence of heart disease. So people who want to decrease their risk of heart disease should reduce their cholesterol intake. Which one of the following, if true, most weakens the argument? ['Any individual resident of a nation whose population has a high average cholesterol intake may have a diet low in cholesterol.', 'The nations with a high average cholesterol intake tend to be among the most impoverished in the world.', 'The nations with high average cholesterol intake are also the countries with the highest levels of unemployment.', 'Individual residents of high cholesterol nations who consume low cholesterol diets have the same rate of heart disease as the national average.']