This MS-900 practice question tests your understanding of describe cloud concepts. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A cloud provider offers virtual machines, but customers must install, configure, and maintain the operating system and applications. Which cloud service model does this describe?
IaaS provides virtualized infrastructure components; the customer controls the OS and applications, matching the described customer responsibility.
B
PaaS (Platform as a Service)
Why wrong: PaaS provides a managed platform where the provider handles the OS, runtime, and middleware, so customers do not manage the OS.
C
SaaS (Software as a Service)
Why wrong: SaaS delivers fully managed applications that the customer accesses via a browser; the provider manages everything, including the application itself.
D
FaaS (Function as a Service)
Why wrong: FaaS, a serverless model, executes individual functions in response to events without provisioning VMs or managing OS.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
IaaS (Infrastructure as a Service)
This scenario describes Infrastructure as a Service (IaaS), where the cloud provider supplies virtualized computing resources such as virtual machines, storage, and networking, but the customer retains full control over the operating system, middleware, and applications. In IaaS, the provider manages only the physical infrastructure (hypervisor, servers, storage, and network), while the customer is responsible for OS installation, configuration, patching, and application management. This aligns directly with the question's description of customer-managed OS and applications on provider-hosted VMs.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
IaaS (Infrastructure as a Service)
Why this is correct
IaaS provides virtualized infrastructure components; the customer controls the OS and applications, matching the described customer responsibility.
Related concept
Read the scenario before looking for a memorised answer.
✗
PaaS (Platform as a Service)
Why it's wrong here
PaaS provides a managed platform where the provider handles the OS, runtime, and middleware, so customers do not manage the OS.
✗
SaaS (Software as a Service)
Why it's wrong here
SaaS delivers fully managed applications that the customer accesses via a browser; the provider manages everything, including the application itself.
✗
FaaS (Function as a Service)
Why it's wrong here
FaaS, a serverless model, executes individual functions in response to events without provisioning VMs or managing OS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse IaaS with PaaS because both involve virtual machines, but PaaS (e.g., Azure App Service) hides the OS and runtime, whereas IaaS requires full customer OS management.
Detailed technical explanation
How to think about this question
Under the hood, IaaS relies on a hypervisor (e.g., VMware ESXi, Microsoft Hyper-V, or KVM) to virtualize physical hardware, presenting virtual machines with virtual CPUs, RAM, and virtual NICs. The customer connects via SSH or RDP to manage the guest OS, which may require manual kernel updates, firewall rules (e.g., iptables or Windows Firewall), and application dependencies. A real-world scenario is migrating an on-premises SQL Server database to an Azure VM (IaaS), where the customer must configure Windows Server, SQL Server, and backup policies, while Azure handles only the physical host and hypervisor failover.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this MS-900 question in full detail.
Describe cloud concepts — This question tests Describe cloud concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: IaaS (Infrastructure as a Service) — This scenario describes Infrastructure as a Service (IaaS), where the cloud provider supplies virtualized computing resources such as virtual machines, storage, and networking, but the customer retains full control over the operating system, middleware, and applications. In IaaS, the provider manages only the physical infrastructure (hypervisor, servers, storage, and network), while the customer is responsible for OS installation, configuration, patching, and application management. This aligns directly with the question's description of customer-managed OS and applications on provider-hosted VMs.
What should I do if I get this MS-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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