What Would Be an Appropriate Explanation for Classifying Clerical and Administrative

What would be an appropriate explanation for classifying clerical and administrative salaries as an indirect cost in the Wood Panel Plant example?

A) those costs are directly associated with this particular training program
B) those costs would have been incurred even if the program were cancelled by management
C) this classification decision was the authors' choice
D) clerical and administrative staff support many different departments, not just HR