Question 69 of 1,020

Mobile Device Accessories →hardMultiple ChoiceObjective-mapped

Thunderbolt 3 vs USB-C Hub for Dual 4K Displays

This 220-1201 practice question tests your understanding of mobile device accessories. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 user has a laptop that supports Thunderbolt 3 and wants to connect two external 4K monitors at full resolution. They currently have a single USB-C hub that only supports DisplayPort over USB-C. What is the most likely limitation?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

A
The laptop's graphics card cannot drive two 4K monitors.
Why wrong: If the laptop supports Thunderbolt 3, it likely has a capable GPU, but the issue is with the hub, not the laptop.
B
The hub does not support Thunderbolt 3 bandwidth.
Thunderbolt 3 requires a compatible dock to deliver the necessary bandwidth (40 Gbps) for dual 4K displays; a standard USB-C hub may only support single display or lower resolutions.
C
The monitors are not compatible with USB-C.
Why wrong: Monitors with DisplayPort or HDMI can be adapted, but the hub's limitation is the bottleneck.
D
The user needs a USB-C to HDMI adapter for each monitor.
Why wrong: Adapters would not solve the bandwidth issue; a Thunderbolt 3 dock is necessary.

Full breakdown with real-world context →

Quick Answer

The answer is that the hub does not support Thunderbolt 3 bandwidth. This is the most likely limitation because Thunderbolt 3 provides up to 40 Gbps of bidirectional bandwidth, which is necessary to drive two 4K displays at full resolution (60 Hz), while a standard USB-C hub using DisplayPort Alt Mode is typically limited to a single 4K output or lower resolutions due to its maximum 10–20 Gbps throughput. On the CompTIA A+ Core 1 220-1201 exam, this question tests your understanding of display connectivity and bandwidth constraints, often appearing as a trap where candidates confuse physical connector compatibility (USB-C) with protocol support (Thunderbolt 3). Remember: just because a USB-C cable fits doesn’t mean it carries Thunderbolt’s full bandwidth—think of USB-C as the shape, Thunderbolt as the speed. A handy memory tip is “Two 4Ks need 40 Gbps—USB-C alone can’t cope.”

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 hub does not support Thunderbolt 3 bandwidth.

Thunderbolt 3 supports up to 40 Gbps bandwidth, which is required to drive two 4K monitors at full resolution (60 Hz) over a single connection. A standard USB-C hub that only supports DisplayPort over USB-C is limited to USB 3.1 Gen 2 (10 Gbps) or USB 3.2 (20 Gbps) bandwidth, which is insufficient to carry two uncompressed 4K video streams simultaneously. Therefore, the hub itself is the bottleneck because it lacks Thunderbolt 3 controller and bandwidth capabilities.

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.

✗
The laptop's graphics card cannot drive two 4K monitors.
Why it's wrong here
If the laptop supports Thunderbolt 3, it likely has a capable GPU, but the issue is with the hub, not the laptop.
✓
The hub does not support Thunderbolt 3 bandwidth.
Why this is correct
Thunderbolt 3 requires a compatible dock to deliver the necessary bandwidth (40 Gbps) for dual 4K displays; a standard USB-C hub may only support single display or lower resolutions.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The monitors are not compatible with USB-C.
Why it's wrong here
Monitors with DisplayPort or HDMI can be adapted, but the hub's limitation is the bottleneck.
✗
The user needs a USB-C to HDMI adapter for each monitor.
Why it's wrong here
Adapters would not solve the bandwidth issue; a Thunderbolt 3 dock is necessary.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The 220-1201 exam often tests the misconception that any USB-C port or hub can deliver full video bandwidth, when in fact only Thunderbolt 3/4 or USB4 hubs with sufficient DisplayPort tunneling can support dual 4K displays at full resolution.

Detailed technical explanation

How to think about this question

Thunderbolt 3 combines PCIe, DisplayPort, and USB data into a single 40 Gbps connection, allowing two 4K displays at 60 Hz via DisplayPort 1.2 (HBR2) or one 5K display. In contrast, a standard USB-C hub using DisplayPort Alt Mode is limited to USB 3.1 Gen 2 (10 Gbps) or USB 3.2 Gen 2x2 (20 Gbps), which can only support a single 4K display at 60 Hz or two at lower resolutions/refresh rates. A real-world scenario is a user connecting a Dell XPS 13 (Thunderbolt 3) to a generic USB-C hub: the hub will negotiate only USB 3.x speeds, failing to enable the second monitor.

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

A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 220-1201 question test?

Mobile Device Accessories — This question tests Mobile Device Accessories — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The hub does not support Thunderbolt 3 bandwidth. — Thunderbolt 3 supports up to 40 Gbps bandwidth, which is required to drive two 4K monitors at full resolution (60 Hz) over a single connection. A standard USB-C hub that only supports DisplayPort over USB-C is limited to USB 3.1 Gen 2 (10 Gbps) or USB 3.2 (20 Gbps) bandwidth, which is insufficient to carry two uncompressed 4K video streams simultaneously. Therefore, the hub itself is the bottleneck because it lacks Thunderbolt 3 controller and bandwidth capabilities.

What should I do if I get this 220-1201 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Same concept, more angles

1 more ways this is tested on 220-1201

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A technician is setting up a mobile workstation for a graphic designer who uses a laptop with a USB-C port that supports Thunderbolt 3. The designer needs to connect two 4K monitors, a wired Ethernet connection, and charge the laptop simultaneously. Which accessory should the technician choose?

hard

A.A USB-C to dual HDMI adapter
✓ B.A Thunderbolt 3 docking station
C.A USB 3.0 hub with HDMI and Ethernet
D.A KVM switch

Why B: A Thunderbolt 3 docking station is the correct choice because it provides sufficient bandwidth (up to 40 Gbps) to drive two 4K monitors simultaneously, includes a dedicated Ethernet port for wired networking, and delivers power delivery (PD) to charge the laptop—all through a single USB-C connection that is backward-compatible with Thunderbolt 3.

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