Choice "A" is correct. Good internal control for cash includes the separation of cash handling, recordkeeping, and reconciliation of bank statements. If the same person who disburses cash (via blank checks and signature plates) also reconciles the bank statement, there is an opportunity for that person to embezzle cash and cover it up.
Choice "d" is incorrect. It is appropriate for the accounts receivable bookkeeper to receive a list of payments prepared by the cashier and make entries in the customers' accounts receivable subsidiary ledger.
Choice "c" is incorrect. It is appropriate for the vouchers payable bookkeeper to match each vendor invoice with the related purchase order and receiving report before approving the voucher for payment.
Choice "b" is incorrect. It is appropriate for the treasurer to examine and cancel vouchers and supporting documentation, and to mail the checks to vendors.