Very small class sizes or very light teaching loads are common in the worst and the best universities. Very small class sizes or very light teaching loads indicate incompetence in classroom instruction. Classes that have very low numbers of students tend to have a lot of classroom discussion. Professors who have very light teaching loads tend to focus their remaining time on research.
It is not good for a university to have class sizes that are very large or very small, or to have professors with teaching loads that are very light or very heavy. After all, crowded classes and overworked faculty cripple the institution' s ability to recruit and retain both qualified students and faculty.
Which one of the following, if added as a premise to the argument, most helps to justify its conclusion?