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MS-900 Practice Question: A company has 50 users with Microsoft 365…
A company has 50 users with Microsoft 365 Business Basic licenses. They want to allow dial-in access to their online meetings for participants who cannot use VoIP. They need to minimize additional licensing costs. What should they purchase?
⚠ Common exam trap
Many exam-takers confuse the Phone System add-on (which handles internal call routing) with Audio Conferencing (which provides external dial-in to meetings), leading them to pick the wrong add-on for PSTN meeting access.
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
✓
Audio Conferencing add-on
Audio Conferencing is the correct add-on because it provides dial-in (PSTN) access to Microsoft Teams meetings, allowing participants to join via phone when VoIP is unavailable. Since the company already has Microsoft 365 Business Basic licenses, which include Teams but not dial-in capabilities, purchasing the Audio Conferencing add-on per user is the most cost-effective way to enable this feature without upgrading the entire license.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Audio Conferencing add-on
Why this is correct
Correct. The Audio Conferencing add-on is the specific Microsoft 365 license that provides a real PSTN phone number (with national and international dial-in numbers) that external participants can call to join a Teams meeting's audio. It is a per-user add-on that works directly with Business Basic, enabling the 50 users to host meetings that anyone can join by phone without installing an app or using a computer.
- ✗
Phone System add-on
Why it's wrong here
Incorrect. Phone System is a cloud-based PBX that grants users an enterprise-grade call handling capability, such as call queues, auto attendants, and the ability to make and receive voice calls from Teams over PSTN (when combined with a Calling Plan). However, it does not provide the dial-in bridge for meetings; without Audio Conferencing, external participants cannot call a number to join an online meeting. Its purpose is to replace an on-premises phone system, not to enable meeting dial-in.
- ✗
Microsoft 365 Business Voice
Why it's wrong here
Incorrect. Microsoft 365 Business Voice is a bundled small-business voice solution that includes Phone System, Audio Conferencing, and a Calling Plan, plus additional features like call queues and auto attendants for an all-in-one phone system. Since the company only needs dial-in conferencing, buying Business Voice for each of the 50 users would be considerably more expensive than adding just the Audio Conferencing add-on. Additionally, Business Voice is designed primarily as a full replacement for a traditional PBX, which is beyond the stated requirement.
- ✗
Upgrade to Microsoft 365 Business Standard
Why it's wrong here
Incorrect. Upgrading from Business Basic to Business Standard adds desktop versions of the Microsoft 365 apps (Word, Excel, PowerPoint, Outlook) and more advanced email/calendar capabilities, but it does not include Audio Conferencing. Microsoft sells Audio Conferencing as a separate add-on regardless of the subscription tier, so the upgrade would not fulfill the dial-in phone access requirement. Consequently, you would still need to purchase the Audio Conferencing add-on on top of the upgrade, making it an extra cost without solving the user's meeting access problem.
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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
Microsoft Teams
Microsoft Teams is a collaboration platform that integrates chat, video meetings, file storage, and application integration into a single workspace, primarily used within the Microsoft 365 ecosystem.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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