What occured at U.S. Foodservices that led to the auditors not discovering an $800 million overstatement in inventories?

Company convinced the suppliers to return fradulent confirmations to the auditors.

The auditors allowed company recieve confirmations from suppliers thus allowing the company to change them.

Company provided auditors with ficticious "shell" companies to send confirmations to allowing the company to confirm its own inventories.

None of the above occured at U.S. Foodservices.