- A
The monitor's resolution is set too high for VGA
Why wrong: VGA can support high resolutions, but blurriness from resolution would be consistent, not specific to one computer.
- B
There is a ground loop between the computer and monitor
A ground loop can cause interference in analog VGA signals, resulting in blurriness and horizontal lines.
- C
The VGA port on the computer has bent pins
Why wrong: Bent pins would cause missing colors or no display, not a blurry image with lines.
- D
The graphics driver is corrupt
Why wrong: A corrupt driver would cause artifacts or crashes, not a specific analog interference pattern.
Question 979 of 1,020
Troubleshooting VGA Blurry Image and Horizontal Lines Due to Ground Loop
This 220-1201 practice question tests your understanding of display devices. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 complains that their external monitor connected via VGA shows a slightly blurry image with faint horizontal lines. The monitor works perfectly with another computer using the same VGA cable. What is the most likely cause?
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.
Quick Answer
The answer is a ground loop between the computer and monitor. This is correct because VGA is an analog signal, and when two devices are plugged into different electrical outlets, a difference in ground potential can create a ground loop, introducing electrical noise that manifests as a blurry image with faint horizontal lines. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of analog video interference versus digital signal issues; a common trap is to blame the cable or monitor when they are proven to work elsewhere. Remember that ground loop interference is unique to analog connections like VGA, where the signal is susceptible to electrical noise from the power supply. A helpful memory tip: think of the horizontal lines as “ground lines” — if the monitor and cable are fine, the loop is in the ground.
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
✓
There is a ground loop between the computer and monitor
The faint horizontal lines and blurry image are classic symptoms of a ground loop, where a difference in electrical potential between the computer and monitor causes interference on the analog VGA signal. Since the monitor works perfectly with another computer using the same cable, the cable and monitor are exonerated, isolating the issue to the computer's grounding or power supply.
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 monitor's resolution is set too high for VGA
Why it's wrong here
VGA can support high resolutions, but blurriness from resolution would be consistent, not specific to one computer.
- ✓
There is a ground loop between the computer and monitor
Why this is correct
A ground loop can cause interference in analog VGA signals, resulting in blurriness and horizontal lines.
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 VGA port on the computer has bent pins
Why it's wrong here
Bent pins would cause missing colors or no display, not a blurry image with lines.
- ✗
The graphics driver is corrupt
Why it's wrong here
A corrupt driver would cause artifacts or crashes, not a specific analog interference pattern.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between analog interference (ground loops) and digital signal issues (bent pins, driver corruption), trapping candidates who assume any display artifact must be a hardware or driver problem rather than an electrical one.
Detailed technical explanation
How to think about this question
Ground loops occur when the computer and monitor are plugged into different electrical outlets with differing ground potentials, creating a 50/60 Hz hum that modulates the analog VGA signal. This interference manifests as faint horizontal bars (hum bars) that slowly scroll or remain static, and can be resolved using a ground loop isolator on the VGA cable or ensuring both devices share the same power circuit.
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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Display Devices — study guide chapter
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Display Devices — This question tests Display Devices — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: There is a ground loop between the computer and monitor — The faint horizontal lines and blurry image are classic symptoms of a ground loop, where a difference in electrical potential between the computer and monitor causes interference on the analog VGA signal. Since the monitor works perfectly with another computer using the same cable, the cable and monitor are exonerated, isolating the issue to the computer's grounding or power supply.
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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Last reviewed: Jul 4, 2026
This 220-1201 practice question is part of Courseiva's free CompTIA 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 220-1201 exam.
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