Infrastructure as a Service (IaaS) provides the most granular control over the computing environment among the three primary cloud service models. In an IaaS model, the cloud provider manages the physical hardware, but the consumer is responsible for deploying and running arbitrary software, which includes operating systems and applications. This gives the organization complete control over the OS, installed applications, storage, and virtual network components like firewalls and load balancers. This level of control and flexibility is the primary reason an organization with specific configuration requirements for its custom application would choose IaaS over PaaS or SaaS, which abstract these underlying layers.

A. This describes Platform as a Service (PaaS), which offers a platform with prebuilt services (e.g., databases, runtimes) to simplify application development and deployment.

B. Performance is not inherently guaranteed by the service model; it depends on the specific resource allocation, architecture, and configuration, which can be tuned in any model.

C. This is incorrect. IaaS requires the customer to provision and manage virtualized compute, storage, and network resources, not eliminate their management entirely.

1. Mell, P., & Grance, T. (2011). The NIST Definition of Cloud Computing (NIST Special Publication 800-145). National Institute of Standards and Technology.

Section 2, "Essential Characteristics, Service Models, and Deployment Models": Defines IaaS as the capability where "The consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components (e.g., host firewalls)." This directly supports option D.

2. Armbrust, M., Fox, A., Griffith, R., Joseph, A. D., Katz, R., Konwinski, A., ... & Zaharia, M. (2010). A view of cloud computing. Communications of the ACM, 53(4), 50-58. https://doi.org/10.1145/1721654.1721672

Page 51, "Classes of Utility Computing": The paper describes IaaS (using the term "Hardware-as-a-Service") as a model where users are given "raw virtualized hardware" on which they can "install any OS and application software." This reinforces the concept of user control over the OS and software stack, aligning with option D.

3. Microsoft Azure Documentation. (n.d.). What is Infrastructure as a service (IaaS)? Microsoft.

"IaaS vs. PaaS vs. SaaS" section: The documentation presents a chart showing that in IaaS, the customer manages "Applications," "Data," "Runtime," "Middleware," and "O/S." This contrasts with PaaS and SaaS, where the vendor manages more of these layers, explicitly demonstrating the control IaaS provides. This supports the reasoning for both the correct answer and the incorrectness of other options.