Editorial: The city has chosen a contractor to upgrade the heating systems in public buildings. Only 40 percent of the technicians employed by this contractor are certified by the Heating Technicians Association. So the city selected a contractor 60 percent of whose technicians are unqualified, which is an outrage. Which one of the following is an assumption required by the argument in the editorial? ['Qualified technicians installed the heating systems to be upgraded.', 'Technicians who lack certification are not qualified technicians.', 'The contractor hired by the city has personal ties to city officials.', 'There are no contractors with fewer than 40 percent of their technicians certified.']