What Is the Major Conceptual Flaw in the "Percentage of Sales

What is the major conceptual flaw in the "percentage of sales" method of budgeting for training?

A) there is no way to know whether a percent of sales is sufficient
B) resources are unfairly allocated
C) years with high sales will generate high training budgets and years with low sales will generate low training budgets
D) agents who make more sales are required to have more training
E) there is no conceptual flaw in the 'percentage of sales' budgeting method