A cloud engineer needs a solution to deploy applications on a cloud without being able to manage and control the server OS. Which type of cloud environment should be used?

IaaS (Infrastructure as a Service) provisions virtual machines where the customer is fully responsible for installing, patching, and managing the guest OS, which directly contradicts the requirement.

Platform as a Service (PaaS) abstracts the OS, runtime, middleware, and infrastructure layers from the consumer. The engineer deploys application code and configuration directly to the platform while the provider handles OS patching, scaling, and server management - meaning the engineer never gains access to or responsibility for the underlying server OS, which is exactly the constraint described.

DaaS (Desktop as a Service) provides virtualized end-user desktop environments and is not a platform for engineers to deploy custom applications.

SaaS (Software as a Service) delivers fully managed applications to end users for consumption and does not provide any mechanism for engineers to deploy or host their own application code.