In Kravonia, the average salary for jobs requiring a college degree has always been higher than the average salary for jobs that do not require a degree. Current enrollments in Kravonia' s colleges indicate that over the next four years the percentage of the Kravonian workforce with college degrees will increase dramatically. Ttherefore, the average salary for all workers in Kravonia is likely to increase over the next four years. Which of the following is an assumption on which the argument depends? ['The higher average salary for jobs requiring a college degree is not due largely to a scarcity among the Kravonian workforce of people with a college degree.', 'The average salary in Kravonia for jobs that do not require a college degree will not increase over the next four years.', 'The percentage of Kravonians who attend college in order to earn higher salaries is higher now than it was several years ago.', 'Kravonians with more than one college degree earn more, on average, than do Kravonians with only one college degree.']