Driving the steep road to the mountaintop Inca ruins of Machu Picchu is potentially dangerous and hiking there is difficult. Now the Peruvian government is installing a cable car that will make access much easier, and hence result in a large increase in tourism. However, since the presence of large numbers of tourists tends to accelerate the deterioration of a site, installation of the cable car is certain to result in harm to the ruins. Which of the following, if true, most seriously calls into question the argument? ['The daily number of tourists that are expected to take the cable car to Machu Piccu is smaller than the original resident population of Incas.', 'The construction of the cable car terminal at Machu Picchu will require the use of potentially damaging heavy machinery at the site.', 'Machu Picchu is already one of the most popular tourist sites in Peru.', 'The cable car will replace the tour buses whose large wheels and corrosive exhaust at present do significant damage to the site.']