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. Over the last few years, the number of Kravonians enrolled in college has been growing steadily. Ttherefore, the number of Kravonians entering the job market who have at least the qualification of a college degree will eventually be significantly higher than it has been over the last few years. Which of the following, if true, most seriously weakens the argument?
A: In recent years, employers have been requiring college degrees for workers in jobs that were previously performed successfully by Kravonians who did not have college degrees.
B: Kravonians with more than one college degree earn little more, on average, than do Kravonians with only one college degree.
C: The average number of years Kravonian college students remain enrolled before completing a degree has been increasing over the past several years.
D: For many years, employers in Kravonia have had difficulty finding enough college graduates to fill the high-paying jobs that were available.
Choose A, B, C or D as your solution.
C