Your organization is deploying a multi-tier web application on GCP. You need to ensure that only authorized internal users can access the application's admin panel. Which GCP service would you utilize for this purpose?

*Explanation:* To restrict access to the admin panel of a multi-tier web application on GCP to authorized internal users, the ideal GCP service to use is **Cloud Identity-Aware Proxy (IAP)**. Cloud IAP provides identity-based access controls and authentication, ensuring that only authenticated and authorized users can access protected resources. It adds an additional layer of security to your applications without requiring significant changes to your application code or infrastructure. The other options (B, C, D, E) are not specifically designed for this purpose and may not provide the same level of access control and security.