Chapter 2, Problem 3Q

I want to verify I'm doing this correctly. If not, please expalin why.

Can someone please verify if my answer is correct and explain why if it is not. thank you.

Which of the following control procedures mitigates the threat of duplicate payments? Select one: a. When an invoice is paid, the invoice and the entire voucher package should be canceled (for example marked “paid”) in a way that it cannot be submitted again. b. When evaluated receipt settlement (invoice-less system) is used, receiving reports need not be marked as paid as no invoices are generated. c. Photocopied invoices can be paid. d. Invoices should be approved for payment only when accompanied by a valid purchase order.