hardMultiple ChoiceObjective-mapped
220-1201 Practice Question: That their external monitor connected via USB-C…
A user reports that their external monitor connected via USB-C (DisplayPort Alt Mode) works intermittently. When it does work, the resolution is limited to 1920x1080 even though the monitor supports 4K. The laptop supports USB-C with DisplayPort Alt Mode. What is the most likely cause?
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 USB-C cable is not rated for video or high-speed data.
USB-C cables vary widely in capability; many only support USB 2.0 data speeds and lack the high-speed lanes needed for 4K video. For 4K over USB-C, the cable must be rated for DisplayPort Alt Mode and high bandwidth (e.g., USB 3.1 Gen 2 or Thunderbolt 3). A cable that only supports USB 2.0 will limit resolution and cause intermittent connectivity.
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 USB-C port is damaged.
Why it's wrong here
A physically damaged USB-C port typically manifests as a complete lack of connection, intermittent connection with severe visual artifacts, or power delivery issues. The consistent ability to display 1080p, even with dropouts, suggests the port is largely functional but encountering a bandwidth or signal integrity issue elsewhere. Therefore, a cable limitation is a more probable cause than outright port damage, which would likely prevent any stable video output.
- ✗
The monitor's USB-C input is set to a lower resolution in its OSD.
Why it's wrong here
If the monitor's On-Screen Display (OSD) were configured to a lower resolution like 1080p, the display would consistently output at that resolution without attempting 4K or experiencing intermittent dropouts. OSD settings are static configurations that dictate a fixed display mode. They do not cause dynamic or intermittent resolution changes or signal loss, which points away from a user-configured setting as the primary issue.
- ✓
The USB-C cable is not rated for video or high-speed data.
Why this is correct
Many generic USB-C cables are designed primarily for charging or USB 2.0 data transfer, lacking the necessary internal wiring and shielding for high-bandwidth video signals like 4K via DisplayPort Alternate Mode. When such a cable is used for 4K video, it either defaults to a lower resolution it can handle, such as 1080p, or experiences signal degradation and intermittent dropouts due to insufficient bandwidth or signal integrity. This precisely matches the user's reported symptoms of intermittent 1080p operation.
- ✗
The graphics driver needs to be updated to support 4K over USB-C.
Why it's wrong here
Graphics drivers manage the software interface between the operating system and the GPU, enabling features and optimizing performance, but they cannot overcome fundamental hardware limitations of a cable. Since the laptop already supports 4K resolution via other output ports, the core graphics capability is present. Therefore, a driver update would not resolve a physical bandwidth constraint imposed by an inadequate USB-C cable, which is a hardware limitation.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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