Which of the following controls is most likely to help ensure that all credit revenue transactions of an entity are recorded?

a. The billing department supervisor sends a copy of each approved sales order to the credit department for comparison to the customer's au- thorized credit limit and current account balance.

b. The accounting department supervisor independently reconciles the accounts receivable subsidiary ledger to the accounts receivable con- trol account each month.

c. The accounting department supervisor controls the mailing of monthly statements to customers and investigates any differences reported by customers.

d. The billing department supervisor matches prenumbered shipping documents with entries in the sales journal.