MS-900 Describe Microsoft 365 apps and services Practice Question
A company uses Microsoft 365 Business Premium. They want to deploy a cloud-based phone system for their employees. Which TWO services should they use?
⚠ Common exam trap
Many candidates confuse Teams Audio Conferencing (meeting dial-in) with the phone system, or think Direct Routing is a cloud-only option when it actually requires on-premises hardware.
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
✓
Calling Plan
Microsoft Teams Phone System (formerly Cloud PBX) provides the core PBX functionality—call control, voicemail, and auto attendants—while a Calling Plan (Microsoft's first-party PSTN connectivity) supplies the phone numbers and minutes to make/receive external calls. Together they form a complete cloud phone system without any on-premises infrastructure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Teams Audio Conferencing
Why it's wrong here
Teams Audio Conferencing is designed for meeting participants to dial into a meeting via telephone, using a hosted audio bridge. It does not provide a user with an assignable phone number or enable one-on-one PSTN calls through the Teams Phone System. Audio Conferencing and Calling Plan are separate add-ons with different purposes, so selecting it would fail to meet the company's phone system requirement.
- ✗
Direct Routing
Why it's wrong here
Direct Routing is an option for connecting the Teams Phone System to an existing carrier infrastructure via a Session Border Controller (SBC), but it is not a core component of the phone system itself. The company using Microsoft 365 Business Premium can choose Direct Routing as an alternative to a Calling Plan, but the question asks for the two foundational services required: Phone System and a PSTN connectivity service. Since Direct Routing is a deployment approach rather than a mandatory building block, it is not one of the required core components.
- ✓
Calling Plan
Why this is correct
A Calling Plan is the Microsoft-provided PSTN service that assigns a phone number and includes a pool of domestic or international minutes to make and receive external calls. It pairs directly with the Teams Phone System, and it is the simplest way to enable cloud calling in Microsoft 365 Business Premium. Without a Calling Plan (or Direct Routing), users can only make internal Teams calls, so it is a correct core component.
- ✗
Microsoft Bookings
Why it's wrong here
Microsoft Bookings is an appointment scheduling application that lets customers book meetings, not a telephony service. It has no relation to the Teams Phone System or PSTN calling and does not provide call routing, voicemail, or phone numbers. Including Bookings would be like adding a calendar mismatch; it doesn't fulfill the company's requirement for a phone system infrastructure.
- ✓
Microsoft Teams Phone System
Why this is correct
The Teams Phone System is the cloud-based PBX that provides call control features such as call transfer, hold, voicemail, and advanced call routing. It is a required service for making and receiving phone calls within Teams, while the Calling Plan supplies the actual phone numbers and minutes. Business Premium includes Teams, but you still need to license Phone System and add a connectivity option, making it one of the two correct components.
Go deeper
Related to this question
Learn chapter
OneDrive for Business
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
This MS-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 MS-900 exam.