Automobile ownership was rare in Sabresia as recently as 30 years ago, but with continuing growth of personal income there, automobile ownership has become steadily more common. Consequently, there are now far more automobiles on Sabresia' s roads than there were 30 years ago, and the annual number of automobile accidents has increased significantly. Yet the annual number of deaths and injuries resulting from automobile accidents has not increased significantly. Which of the following, if true, most helps to explain why deaths and injuries resulting from automobile accidents have not increased significantly? ['Because of a vigorous market in used cars, the average age of cars on the road has actually increased throughout the years of steady growth in automobile ownership.', "The increases in traffic volume have been most dramatic on Sabresia's highways, where speeds are well above those of other roads.", 'Automobile ownership is still much less common in Sabresia than it is in other countries.', 'With more and more people owning cars, the average number of passengers in a car on the road has dropped dramatically.']