* Why Controller?
* A customcontrollerallows:
* Complex validation involving multiple objects.
* Redirection to another Visualforce page upon success.
* Controllers can implement custom save logic and redirect usingPageReference.
* Why Not Other Options?
* A. Apex: Apex is the underlying programming language, but a controller specifically handles the Visualforce logic.
* B. Trigger: Triggers execute on DML events, not on button clicks in Visualforce.
* D. Extension: Extensions enhance standard controllers but are not necessary here since a custom controller is being built.
References:Controllers and Extensions:https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_controller_custom.htm