Which service model includes everything from IaaS, plus operating systems and allows the vendor to handle maintenance?

The correct choice encompasses the features presented within the Infrastructure as a Service (IaaS) model while additionally incorporating the operating system layer. This means that the vendor not only supplies basic infrastructure like virtual machines and storage but also provides a platform for developers to build, manage, and deploy applications.

In the Platform as a Service (PaaS) model, users benefit from a complete development environment that includes operating systems and middleware, thus relieving them of the complexities involved in maintaining the underlying hardware or software stack. This allows developers to focus on coding and application development without worrying about server maintenance or software updates.

The other options lack this combined offering. IaaS typically includes only the infrastructure components, without the operating systems or higher-level services. Software as a Service (SaaS) delivers fully functional applications over the internet, where the user interacts with the software without needing to manage the underlying platform. Hybrid Cloud, on the other hand, refers to a combination of public and private cloud resources, but does not specify a service model, and encompasses multiple models rather than a singular one. Thus, PaaS is the model that most accurately includes IaaS components along with operating system management.