A company that requires full administrative control at the OS level is considering the use of public cloud services. Which of the following service models would BEST fit the company's requirements?

SaaS (Software as a Service) delivers fully managed applications over the internet, granting users no access to the underlying OS or infrastructure.

DBaaS (Database as a Service) exposes only database management interfaces, not OS-level access or configuration.

PaaS (Platform as a Service) manages the underlying OS and runtime on behalf of the customer, leaving only application deployment in the customer's control.

IaaS (Infrastructure as a Service) delivers virtualized compute, storage, and networking resources where the customer is responsible for - and has full control over - the operating system, middleware, and applications. This model is ideal for organizations that need root or administrator access to configure and manage the OS directly. Other service models abstract away the OS layer, making IaaS the only option that satisfies this requirement.