Microsoft Certified: Azure Fundamentals (AZ-900) Practice Exam 2025 - Free AZ-900 Practice Questions and Study Guide

The option that comes with the maximum responsibility for the customer is indeed Infrastructure as a Service (IaaS). In an IaaS model, customers are responsible for managing everything from the operating system up to the applications they deploy. This includes not only the operating system but also networking, storage, and servers.

Essentially, IaaS provides the most control to the customer because they have to handle the maintenance and management of the infrastructure while the cloud provider only manages the underlying physical hardware. This model is suited for users who need dynamic and flexible resources, giving them the freedom to manage their IT environment according to their specific needs.

In contrast, Platform as a Service (PaaS) takes care of the underlying infrastructure and the platform where applications run, allowing customers to focus more on application development rather than hardware management. Software as a Service (SaaS) abstracts even further, where the provider manages everything, including applications, and users simply access the software over the internet.

In summary, with IaaS, customers bear the most responsibility compared to PaaS and SaaS, making it the correct answer for maximum customer responsibility.