Large-Scale Reductions in Class Size Will Likely Lower the Average

Large-scale reductions in class size will likely lower the average quality of teachers: first, because to hire additional teachers school districts must reach into the lower-quality segment of the teacher pool; and, second, because a given budget will be spread among a higher number of teachers, thereby limiting potential increases in teacher salaries. (Jane Hannaway and Robert I. Lerman, Letter to the Editor, The New Republic)
This passage exemplifies a(n) _____.

A) conditional statement
B) explanation
C) unsupported assertion
D) report
E) argument