Which model requires the customer to perform their own systems patching?

The correct choice is based on the responsibilities associated with different cloud service models. In the IaaS (Infrastructure as a Service) model, the customer is responsible for managing and maintaining the operating systems, including performing their own systems patching. This model gives users control over the infrastructure while requiring them to take care of the software and management aspects, such as updates and patches to their operating systems.

In contrast, in the SaaS (Software as a Service) model, the provider manages all aspects of the infrastructure, application, software updates, and patches, so the user does not have to handle those tasks. The PaaS (Platform as a Service) model provides a platform that enables users to develop, run, and manage applications without the complexities of building and maintaining the infrastructure while still requiring some degree of management and maintenance from the user, particularly focused on the applications. DBaaS (Database as a Service) abstracts database management, but like PaaS and SaaS, the user typically has less control over the underlying systems compared to what is offered in an IaaS setup. Thus, IaaS is the model where customers carry the responsibility for systems patching.