Which of the following is an effective internal accounting control over accounts receivable?

(a) Only people who handle cash receipts should be responsible for preparing documents that reduce accounts receivable balances.

(b) Responsibility for approval of the write-off of uncollectible accounts receivable should be assigned to the cashier.

(c) Balances in the subsidiary accounts receivable ledger should be reconciled to the general ledger control account once a year, preferably at yearend.

(d) The billing function should be assigned to people other than those responsible for maintaining accounts receivable subsidiary records.