You have an accounting application named App1 that depends on a legacy database. You're planning to move App1 to the cloud. Which cloud service model should you use?

IaaS is the correct choice because it provides the most control over the underlying infrastructure, allowing you to migrate legacy applications like App1 that have specific dependencies (e.g., an older database version or operating system) without significant refactoring. You provision virtual machines and networks, then install your application and database as you would on-premises. PaaS would require modifying App1 to fit the platform's specific services and frameworks, which might not be feasible for a legacy application. SaaS is a fully managed application where you have no control over the underlying infrastructure or application code, making it unsuitable for migrating an existing custom application.