You are perfoming security testing on an existing asp.net web page.You notice that you are able to issue unauthorised postback requests to the page. You need to prevent unauthorised post back requests. which page directive you use？（）
- A<%@Page strict = "true" %>
- B<%@Page enableViewStateMac = "true" %>
- C<%@Page EnableEventValidation = "true" %>
- D<%@Page Aspcompact = "true" %>