* Validation Rule Violations:
* Salesforce automatically throws exceptions for validation rule violations during DML operations.
* <apex:messages> is used to display these errors to the user.
* Why Not Other Options?
* A: Controller attributes alone cannot handle validation messages.
* B: A try/catch block does not address validation rule violations effectively.
* D: Database.upsert() method is not related to validation error handling.
* Apex Messages: https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages
/pages_compref_messages.htm
References: