Archaeologist: The extensive network of ancient tracks on the island of Malta was most likely created through erosion caused by the passage of wheeled vehicles. Some researchers have suggested that the tracks were in fact manually cut to facilitate the passage of carts, citing the uniformity in track depth. However, this uniformity is more likely indicative of wheel diameter: Routes were utilized until tracks eroded to a depth that made vehicle passage impossible. Which one of the following is the overall conclusion of the archaeologist's argument? ['The extensive network of ancient tracks on the island of Malta was most likely created through erosion caused by the passage of wheeled vehicles.', 'The uniformity of depth of the ancient tracks on the island of Malta is probably indicative of the wheel diameter of the carts that passed over them.', 'Some researchers have suggested that the ancient tracks on the island of Malta were in fact manually cut to facilitate the passage of carts.', 'Some researchers cite the uniformity of the depth of the ancient tracks on the island of Malta to support the suggestion that they were manually cut.']