- A
Microsoft, because they manage all operating system updates in Azure.
Why wrong: This is incorrect. Microsoft manages the underlying physical infrastructure and the host OS, but not the guest OS inside a customer's virtual machine.
- B
The customer, because the customer manages the guest operating system and is responsible for patching it.
This is correct. In IaaS, the customer is responsible for maintaining the guest OS, including applying security patches and updates.
- C
Both Microsoft and the customer share responsibility equally for operating system patching.
Why wrong: This is incorrect. Although responsibility is shared in the cloud model, it is not an equal split; the customer is solely responsible for the guest OS patching, while Microsoft handles the infrastructure layer.
- D
The cloud service provider, as a general rule for all services in Azure.
Why wrong: This is incorrect. The term 'cloud service provider' is vague; for IaaS, the customer manages the OS. Responsibility varies by service model (IaaS, PaaS, SaaS).
AZ-900 Describe cloud concepts Practice Question
This AZ-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 company plans to migrate a line-of-business application to Azure. The application will run on a virtual machine (IaaS). The company wants to ensure that the operating system is kept up to date with security patches. According to the shared responsibility model, who is primarily responsible for applying these patches?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The customer, because the customer manages the guest operating system and is responsible for patching it.
In the shared responsibility model for IaaS, the customer retains control over the guest operating system, including applying security patches. Microsoft manages the physical host and hypervisor but does not patch the OS running inside the VM. Therefore, the customer is primarily responsible for keeping the OS up to date.
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.
- ✗
Microsoft, because they manage all operating system updates in Azure.
Why it's wrong here
This is incorrect. Microsoft manages the underlying physical infrastructure and the host OS, but not the guest OS inside a customer's virtual machine.
- ✓
The customer, because the customer manages the guest operating system and is responsible for patching it.
Why this is correct
This is correct. In IaaS, the customer is responsible for maintaining the guest OS, including applying security patches and updates.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Both Microsoft and the customer share responsibility equally for operating system patching.
Why it's wrong here
This is incorrect. Although responsibility is shared in the cloud model, it is not an equal split; the customer is solely responsible for the guest OS patching, while Microsoft handles the infrastructure layer.
- ✗
The cloud service provider, as a general rule for all services in Azure.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume Microsoft handles all patching in Azure because of the 'as a service' nature, but in IaaS, the customer retains full control and responsibility for the guest OS.
Detailed technical explanation
How to think about this question
Under the hood, Azure VMs run on Hyper-V hosts managed by Microsoft. The guest OS runs in a separate partition with no direct access to the host. Microsoft applies patches to the host OS and hypervisor via Azure's automated update processes, but the guest OS is isolated and must be patched by the customer using tools like Windows Update, Azure Update Manager, or third-party patch management solutions. A real-world scenario: if a critical vulnerability like CVE-2021-1678 affects the guest OS, the customer must deploy the patch; Microsoft will not apply it automatically.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this AZ-900 question test?
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: The customer, because the customer manages the guest operating system and is responsible for patching it. — In the shared responsibility model for IaaS, the customer retains control over the guest operating system, including applying security patches. Microsoft manages the physical host and hypervisor but does not patch the OS running inside the VM. Therefore, the customer is primarily responsible for keeping the OS up to date.
What should I do if I get this AZ-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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Last reviewed: Jun 11, 2026
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.
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