A startup wants a service model where they don't manage any infrastructure or applications. Which should they use?

SaaS (Software as a Service) is the correct choice because it provides a complete, ready-to-use application managed entirely by the vendor. Users simply access the software over the internet, eliminating the need to manage any underlying infrastructure, operating systems, or even the application itself. This aligns perfectly with the startup's goal of not managing infrastructure or applications. PaaS (Platform as a Service) allows developers to deploy, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app, but the user is still responsible for the application code and data. IaaS (Infrastructure as a Service) provides virtualized computing resources over the internet, giving users control over operating systems, applications, and middleware, but they still manage those components. A hybrid cloud combines public and private cloud environments, which is a deployment model, not a service model that dictates management responsibility.