SPC Corporation sells computer security software. They maintain their AIS using general ledger software; data files are backed up twice a day. Sales staff can access the customer database, inventory files and general ledger, as well as sales-related documents such as invoices and sales orders. Newly hired sales staff members at SPC receive the company procedures manual which explains the process used to complete the steps in the sales/collection process. To minimize costs, SPC designates up to five sales staff members each month who can do credit checks for all new customers in addition to processing sales. SPC bills its clients monthly and uses the balance forward method of accounting for receivables; all cash receipts from clients are processed using a lockbox procedure. The lockbox firm's fee is 3% of all collections. SPC's accounting department estimates bad debts at the end of each fiscal year; they are normally about 1% of total sales. Based on its risk exposures, SPC would benefit most from implementing which of the following internal controls?

A. Cross-training employees

B. Separation of duties

C. Normalized database files

D. Use of the COSO internal control framework