Which service model provides server infrastructure in the cloud?

Infrastructure as a Service (IaaS) is the correct choice as it specifically provides virtualized computing resources over the internet. In this model, cloud providers manage the physical infrastructure, such as servers, storage, and networking, while the user has control over the operating systems and applications running on those resources. This allows users to provision and scale resources as needed without the hassle of maintaining physical hardware.

In contrast, Platform as a Service (PaaS) offers a platform allowing developers to build, deploy, and manage applications without dealing with the underlying infrastructure; here, the focus is on providing a development environment and tools rather than bare infrastructure. Software as a Service (SaaS) delivers software applications over the internet, managed by the provider, meaning users access applications rather than managing the infrastructure. Data as a Service (DaaS) emphasizes providing data storage and management solutions, dealing with data specifically rather than the underlying infrastructure itself.

This differentiation highlights why IaaS is the appropriate model for server infrastructure in the cloud.