The correct place to implement CSRF (Cross-Site Request Forgery) protection validation is: C. In the controller function that handles the submitted form - When the form is submitted, the controller function that processes the form data should include a check for a valid CSRF token. This is typically done using the validateRequest or validateAjaxRequest method depending on the nature of the request (synchronous or asynchronous). By performing this validation in the controller function that handles the form submission, it ensures that the form data is protected against CSRF attacks, which is a critical security measure for forms that perform changes to server-side data.