This MS-900 practice question tests your understanding of describe cloud concepts. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 a service where customers can provision virtual machines, storage, and networks on-demand through a web portal. The customer is responsible for patching the guest operating system. Which cloud service model best describes this offering?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Why wrong: Incorrect. In SaaS, the provider manages the entire application stack, including OS patching.
B
Platform as a Service (PaaS)
Why wrong: Incorrect. In PaaS, the provider manages the runtime environment and typically patches the OS, leaving the customer to focus on application code.
C
Infrastructure as a Service (IaaS)
Correct. The customer provisions the VMs and is responsible for OS updates and patches, while the provider manages the underlying hardware.
D
Desktop as a Service (DaaS)
Why wrong: Incorrect. DaaS delivers virtual desktop environments, not general-purpose VMs, and the provider typically manages the OS.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Infrastructure as a Service (IaaS)
The correct answer is C (Infrastructure as a Service) because the customer provisions fundamental compute, storage, and networking resources on-demand, and retains control over the guest OS, including patching. In IaaS, the provider manages only the physical infrastructure (hypervisor, networking, storage hardware), while the customer is responsible for the OS and applications, matching the scenario exactly.
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.
✗
Software as a Service (SaaS)
Why it's wrong here
Incorrect. In SaaS, the provider manages the entire application stack, including OS patching.
✗
Platform as a Service (PaaS)
Why it's wrong here
Incorrect. In PaaS, the provider manages the runtime environment and typically patches the OS, leaving the customer to focus on application code.
✓
Infrastructure as a Service (IaaS)
Why this is correct
Correct. The customer provisions the VMs and is responsible for OS updates and patches, while the provider manages the underlying hardware.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Desktop as a Service (DaaS)
Why it's wrong here
Incorrect. DaaS delivers virtual desktop environments, not general-purpose VMs, and the provider typically manages the OS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse PaaS with IaaS because both involve 'platform' or 'infrastructure' terms, but the key differentiator is who patches the guest OS — in PaaS, the provider patches it, while in IaaS, the customer does.
Detailed technical explanation
How to think about this question
Under the hood, IaaS relies on a hypervisor (e.g., Hyper-V, VMware ESXi) to virtualize hardware, exposing virtual NICs, virtual disks, and virtual CPUs to the guest OS. The customer interacts via APIs (e.g., Azure Resource Manager, AWS EC2 API) to provision resources, and the provider uses Software-Defined Networking (SDN) and storage virtualization to isolate tenants. A real-world scenario: a company migrating an on-premises SQL Server to Azure VMs must still apply Windows Update patches and SQL Server service packs, as Azure only patches the host OS (Hyper-V) and physical hardware.
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: Infrastructure as a Service (IaaS) — The correct answer is C (Infrastructure as a Service) because the customer provisions fundamental compute, storage, and networking resources on-demand, and retains control over the guest OS, including patching. In IaaS, the provider manages only the physical infrastructure (hypervisor, networking, storage hardware), while the customer is responsible for the OS and applications, matching the scenario exactly.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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