Which of the following situations represents a strength in the internal control for purchasing and accounts payable?

a. Prenumbered receiving reports are issued randomly.

b. Invoices are approved for payment by the purchasing department.

c. Unmatched receiving reports are reviewed annually.

d. Vendors' invoices are matched against purchase orders and receiving reports before a liability is recorded.

e. The purchasing department reconciles the accounts payable subsidiary vendor ledger with the general ledger control account.