The average life expectancy of the population of Japan has risen steadily since 1960 and is now the highest national average in the world, even though heart disease among the Japanese has increased since they began to eat more of the fatty foods typical of the diets of people in Western countries. Which of the following, if true, best helps to explain the steady rise in life expectancy that is cited above? ['Since 1960 the decline in illnesses that kill more Japanese people than does heart disease has been greater than the increase in heart disease.', 'The life-style of some Japanese people includes regular exercise, which is thought to help the heart resist the loss of strength that accompanies aging.', 'The average Westerner is still five times more likely to develop heart disease than is the average Japanese person.', 'The Japanese diet has traditionally included many nonfatty foods that are thought to reduce the risk of developing heart disease.']