- A
Purchase Microsoft 365 E5 add-on for each user
Why wrong: The E5 add-on provides many additional security and compliance features not required, making it more expensive than the targeted add-on.
- B
Purchase Phone System add-on and Audio Conferencing add-on separately for each user
Why wrong: Buying two separate add-ons is more expensive than purchasing the combined 'Phone System + Audio Conferencing' add-on.
- C
Purchase the 'Phone System + Audio Conferencing' add-on for each user
This combined add-on includes both Phone System and Audio Conferencing at a lower cost than purchasing individually.
- D
Upgrade all users to Microsoft 365 E5
Why wrong: Upgrading to E5 is a full license upgrade, which is significantly more expensive than adding the targeted add-on to existing E3 licenses.
Microsoft 365 E3 Phone System + Audio Conferencing Add-On — Cost-Effective PSTN
This MS-900 practice question tests your understanding of describe microsoft 365 pricing and support. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: phone System + Audio Conferencing add-on. 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 currently has Microsoft 365 E3 licenses for all 200 users. They need to add Microsoft Teams Phone System capabilities for call control and PBX features, and they want to allow dial-in audio conferencing for online meetings. They want to minimize additional costs while keeping existing E3 subscriptions. What is the most cost-effective licensing strategy?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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 the 'Phone System + Audio Conferencing' add-on for each user
Option C is correct because the bundled 'Phone System + Audio Conferencing' add-on provides both Teams Phone System (call control and PBX features) and dial-in Audio Conferencing at a lower combined cost than buying the two add-ons separately (option B). Note that PSTN connectivity itself (a Calling Plan, Operator Connect, or Direct Routing) is licensed separately from Phone System — the bundle covers the phone system platform and conferencing, which is what the requirement lists. Upgrading to E5 (options A and D) includes these features but costs significantly more per user.
Key principle: Phone System + Audio Conferencing add-on
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 Microsoft 365 E5 add-on for each user
Why it's wrong here
The E5 add-on provides many additional security and compliance features not required, making it more expensive than the targeted add-on.
- ✗
Purchase Phone System add-on and Audio Conferencing add-on separately for each user
Why it's wrong here
Buying two separate add-ons is more expensive than purchasing the combined 'Phone System + Audio Conferencing' add-on.
- ✓
Purchase the 'Phone System + Audio Conferencing' add-on for each user
Why this is correct
This combined add-on includes both Phone System and Audio Conferencing at a lower cost than purchasing individually.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Phone System + Audio Conferencing add-on
- ✗
Upgrade all users to Microsoft 365 E5
Why it's wrong here
Upgrading to E5 is a full license upgrade, which is significantly more expensive than adding the targeted add-on to existing E3 licenses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is confusing Phone System (the call-control platform) with a Calling Plan (the PSTN connectivity). MS-900 tests that these are separate licenses: Phone System add-ons do not automatically include PSTN calling minutes.
Detailed technical explanation
How to think about this question
The 'Phone System + Audio Conferencing' add-on is a single SKU (e.g., SPZA for commercial) that combines the Phone System license (required for PSTN calling) with Audio Conferencing (for dial-in meeting capabilities) and includes a domestic Calling Plan (e.g., 1200 minutes per user per month in the US). Under the hood, this add-on leverages Microsoft's SIP trunking infrastructure and the Teams Direct Routing or Operator Connect for PSTN connectivity, but the bundled SKU simplifies licensing by avoiding separate provisioning of Phone System (e.g., SKU MCOEV) and Audio Conferencing (e.g., SKU MCOMEETADV). A real-world scenario where this matters is when an organization needs to minimize per-user costs while enabling both outbound calling and dial-in conferencing; the bundled add-on is often 20-30% cheaper than purchasing the two add-ons individually.
KKey Concepts to Remember
- Phone System + Audio Conferencing add-on
- Microsoft 365 E3
- PSTN Calling Capabilities
- Audio Conferencing
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
Phone System + Audio Conferencing add-on
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Review phone System + Audio Conferencing add-on, then practise related MS-900 questions on the same topic to reinforce the concept.
- →
Describe Microsoft 365 pricing and support — study guide chapter
Learn the concepts, then practise the questions
- →
Describe Microsoft 365 pricing and support practice questions
Targeted practice on this topic area only
- →
All MS-900 questions
985 questions across all exam domains
- →
Microsoft 365 Fundamentals MS-900 study guide
Full concept coverage aligned to exam objectives
- →
MS-900 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related MS-900 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Describe Microsoft 365 apps and services practice questions
Practise MS-900 questions linked to Describe Microsoft 365 apps and services.
Describe Microsoft 365 pricing, licensing, and support practice questions
Practise MS-900 questions linked to Describe Microsoft 365 pricing, licensing, and support.
Describe cloud concepts practice questions
Practise MS-900 questions linked to Describe cloud concepts.
Describe security, compliance, privacy, and trust in Microsoft 365 practice questions
Practise MS-900 questions linked to Describe security, compliance, privacy, and trust in Microsoft 365.
Describe Microsoft 365 pricing and support practice questions
Practise MS-900 questions linked to Describe Microsoft 365 pricing and support.
MS-900 fundamentals practice questions
Practise MS-900 questions linked to MS-900 fundamentals.
MS-900 scenario practice questions
Practise MS-900 questions linked to MS-900 scenario.
MS-900 troubleshooting practice questions
Practise MS-900 questions linked to MS-900 troubleshooting.
Practice this exam
Start a free MS-900 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this MS-900 question test?
Describe Microsoft 365 pricing and support — This question tests Describe Microsoft 365 pricing and support — Phone System + Audio Conferencing add-on.
What is the correct answer to this question?
The correct answer is: Purchase the 'Phone System + Audio Conferencing' add-on for each user — Option C is correct because the bundled 'Phone System + Audio Conferencing' add-on provides both Teams Phone System (call control and PBX features) and dial-in Audio Conferencing at a lower combined cost than buying the two add-ons separately (option B). Note that PSTN connectivity itself (a Calling Plan, Operator Connect, or Direct Routing) is licensed separately from Phone System — the bundle covers the phone system platform and conferencing, which is what the requirement lists. Upgrading to E5 (options A and D) includes these features but costs significantly more per user.
What should I do if I get this MS-900 question wrong?
Review phone System + Audio Conferencing add-on, then practise related MS-900 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Phone System + Audio Conferencing add-on
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More MS-900 practice questions
- Your company uses Microsoft 365 and wants to ensure that when employees share sensitive documents externally, access is…
- A company is deploying Microsoft 365 Copilot and wants to ensure that only users with the appropriate sensitivity labels…
- A compliance-aware administrator is selecting the right Microsoft 365 capability to use Microsoft 365 and another public…
- Which THREE of the following are included in Microsoft 365 E5 compliance features? (Choose three.)
- A company currently has Microsoft 365 E3 licenses for all users. They need to retain all Exchange Online mailbox data fo…
- Your organization has a Microsoft 365 E5 subscription and wants to centrally manage security incidents across identities…
Last reviewed: Jun 11, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.