Analysing Days Sales Outstanding (DSO) and the Aging Schedule Are

Analysing days sales outstanding (DSO) and the aging schedule are two common methods for monitoring receivables.However, they can provide erroneous signals to credit managers when

A) Customers' payments patterns are changing.
B) Sales fluctuate seasonally.
C) Some customers take the discount and others do not.
D) Sales are relatively constant, either seasonally or cyclically.
E) None of the above.