You are developing a page named Process.aspx in a shopping cart Web application that will be integrated into Certkiller .com's existing e-Commerce Web site. The Process.aspx page allows customers to pay for purchases using their credit cards. The Process.aspx page contains a Button control that confirms the customer's payment and calls an external Web service that charges the customer's credit card. You must implement confirmation and prevent postback unless the customer confirms payment. What should you do?（）

A. Set the OnClientClick property to a JavaScript statement.
B. Set the PostBackUrl property to a JavaScript statement.
C. Set the PostBackUrl property to the URL of a confirmation page.
D. Set the OnClientClick property to the URL of a confirmation page.