Which of the following control activities would be a reasonable control over the accuracy of recorded sales?

a. The software application matches sales invoice quantities with the underlying packing slip and prices with the sales order.

b. The software application prints a report of unfilled sales orders.

c. The software application prints a report of all bills of lading not matched with a sales invoice.

d. The software application matches the customer number on the sale invoice with the customer number on the sales order.