Which of the following internal control procedures would most likely ensure that all billed sales are correctly posted to the sales ledger?

(a) Each shipment on credit is supported by a pre-numbered sales invoice.

(b) The sales ledger is reconciled daily to the control account in the general ledger.

(c) Each sales invoice is supported by a pre-numbered shipping document.

(d) Daily sales summaries are compared with daily postings to the sales ledger.

Choose the best answer.