An accounts payable clerk in the accounting department prepared a voucher authorizing the payment of an invoice for which goods were never ordered or received. The best control to ensure that this does not happen in the future is to: OA. require that vouchers be supported by a purchase order, receiving report and original invoice. OB. segregate responsibilities within the accounts payable department. OC. require that all accounts payable checks be signed by two officers, OD. sequentially pre-number purchase orders