MS-900 Practice Question: Describe Microsoft 365 pricing, licensing, and support
A customer has 100 users on Microsoft 365 Business Basic and wants to add Microsoft Defender for Office 365 Plan 1. Which licensing approach should they use?
⚠ Common exam trap
Candidates often assume Defender for Office 365 Plan 1 is a standalone product or that it is included in E3, when in fact it is an add-on that requires a qualifying base license and is not bundled with E3.
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
✓
Purchase Microsoft Defender for Office 365 Plan 1 as an add-on for each user
Microsoft Defender for Office 365 Plan 1 is an add-on that can be purchased for users who already have a qualifying subscription like Microsoft 365 Business Basic. It provides advanced threat protection features such as Safe Attachments and Safe Links, and it must be assigned per user on top of an existing Microsoft 365 license. Option C is correct because it directly describes this additive licensing model.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Purchase a separate Microsoft Defender for Office 365 Plan 1 subscription without underlying Microsoft 365 licenses
Why it's wrong here
Microsoft Defender for Office 365 Plan 1 is an add-on, not a standalone service. It must be layered on an active eligible Microsoft 365 plan such as Business Basic for each user, because it has no mailbox or basic email infrastructure of its own. Purchasing it separately without underlying licenses leaves you with no user base to assign the add-on to, violating Microsoft's licensing requirements and providing no functional email protection.
- ✗
Upgrade all users to Microsoft 365 E3
Why it's wrong here
Upgrading all 100 users to Microsoft 365 E3 would indeed provide Defender for Office 365 Plan 1, but it would also force you to pay for Windows 10/11 Enterprise and enterprise mobility and security features that are completely unrelated to email protection. This bundle is priced significantly higher than Business Basic, making it an unnecessarily expensive route to secure only your Exchange Online mailboxes. A targeted add-on is the correct, cost-effective licensing approach for this scenario.
- ✓
Purchase Microsoft Defender for Office 365 Plan 1 as an add-on for each user
Why this is correct
Because Microsoft 365 Business Basic is an eligible base subscription, you can directly purchase Defender for Office 365 Plan 1 as an add-on for each of the 100 users and assign it to them through the Microsoft 365 admin center. This leaves the existing Business Basic licenses untouched, avoids any migration or plan-change overhead, and activates the advanced email threat protection capabilities you need: anti-phishing, anti-spam, and real-time suspicious message detection. With no extra Windows or mobility features, this is precisely the minimal licensing change that fulfills the customer's requirement.
- ✗
Upgrade to Microsoft 365 E5
Why it's wrong here
Microsoft 365 E5 includes Defender for Office 365 Plan 2, which goes far beyond Plan 1 by adding automated investigation and response, simulation training, and advanced threat hunting tools. Those features are not needed in this scenario, and E5's per-user cost is dramatically higher than the sum of a Business Basic plus Plan 1 add-on. Thus, upgrading to E5 would solve the technical gap but create a substantial licensing cost overrun, making it the wrong answer.
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Microsoft 365 Licensing Plans
Key term
Microsoft 365
Microsoft 365 is a subscription-based cloud service from Microsoft that combines productivity tools like Office apps with security, device management, and online storage.
Key term
Subscription
A subscription is a payment model where you pay a recurring fee to access a product or service instead of buying it once and owning it forever.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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