Twelve healthy volunteers with the Apo-A-IV-1 gene and twelve healthy volunteers who instead have the Apo-A-IV-2 gene each consumed a standard diet supplemented daily by a high-cholesterol food. A high level of cholesterol in the blood is associated with an increased risk of heart disease. After three weeks, the blood cholesterol levels of the subjects in the second group were unchanged, whereas the blood cholesterol levels of those with the Apo-A-IV-1 gene rose 20 percent. Which one of the following is most strongly supported by the information above? ['The presence of the Apo-A-IV-2 gene may inhibit the elevation of blood cholesterol.', 'Most of those at risk of heart disease may be able to reduce their risk by adopting a low-cholesterol diet.', 'Approximately half the population carries a gene that lowers cholesterol levels.', 'The presence of the Apo-A-IV-1 gene seems to indicate that a person has a lower risk of heart disease.']