220-1101 Mobile Devices Practice Question
A user reports that their smartphone's touchscreen is unresponsive along the left edge but works fine elsewhere. The technician has already performed a soft reset and checked for screen protectors or debris. Which of the following is the most likely cause?
⚠ Common exam trap
CompTIA often tests the distinction between digitizer (touch input) and LCD (display output), trapping candidates who confuse a touch failure with a display failure or assume software corruption is the cause when hardware is localized.
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
✓
A malfunctioning digitizer
The digitizer is the layer responsible for converting touch input into electrical signals. A partial failure along the left edge indicates a localized digitizer malfunction, as the LCD display and operating system are unaffected. Soft reset and debris checks rule out software or physical obstruction issues, isolating the hardware digitizer as the most likely cause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A malfunctioning digitizer
Why this is correct
The digitizer is a transparent sensing grid layered above (or integrated with) the display that converts finger contact into X/Y coordinates. It is the only component in the stack responsible for touch input, so a break in the leftmost sensing columns or a delamination in that region will create a persistent dead zone along the left edge while the image below remains normal. This matches the symptom exactly because a failed digitizer can lose a contiguous band of coordinates without affecting the other X columns.
- ✗
A failing battery
Why it's wrong here
Battery and power management failures affect the delivery of voltage/current; a weak or failing battery can force shutdowns, cause stale-touch false positives, or make the whole screen unresponsive, but it cannot logically suppress X-axis readings only on the left side. The digitizer's scan lines receive power from the same rails as the rest of the panel, so an under-voltage condition would degrade the entire digitizer grid, not a discrete edge. Thus, a localized dead zone is a physical/electrical break in that specific digitizer column set, not a battery issue.
When this WOULD be correct
A user reports that their smartphone randomly shuts down even when the battery indicator shows 30% charge, and the device fails to power on without being plugged in. In that scenario, a failing battery is the most likely cause.
- ✗
A corrupt operating system
Why it's wrong here
A corrupt operating system, such as one with a failed update or bad touch firmware, affects the software stack that processes input events from the entire touch controller. It has no mechanism to selectively ignore only the left edge of the panel, so it would cause a globally unresponsive touchscreen, driver crashes, or other system-wide malfunctions. Since the reported symptom is a single localized edge, the OS itself is not the cause.
When this WOULD be correct
A corrupt operating system would be correct if the user reports that the smartphone fails to boot, freezes during startup, or experiences persistent app crashes after an update, with no hardware damage or physical symptoms.
- ✗
A damaged LCD display
Why it's wrong here
The LCD is a light-modulating output layer that forms images; it has no touch-detection function and cannot pass a touch coordinate to the phone. If the LCD were damaged, the visible signs would be artifacts like black blotches, white clouds, color banding, or physical cracks, not a clean edge-specific dead zone. Even in in-cell panels that share lamination, the touch-sensing electrodes are part of the digitizer function, so a dead input zone points to that sensor layer, not the imaging function.
When this WOULD be correct
A damaged LCD display would be correct if the user reported visual anomalies such as lines, flickering, or a black screen, rather than touch unresponsiveness. For example: 'A user reports the screen shows vertical lines and flickering after a drop.'
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓A malfunctioning digitizerCorrect answer▾
Why this is correct
The digitizer is a transparent sensing grid layered above (or integrated with) the display that converts finger contact into X/Y coordinates. It is the only component in the stack responsible for touch input, so a break in the leftmost sensing columns or a delamination in that region will create a persistent dead zone along the left edge while the image below remains normal. This matches the symptom exactly because a failed digitizer can lose a contiguous band of coordinates without affecting the other X columns.
✗A failing batteryWrong answer — click to see why▾
Why this is wrong here
A failing battery typically causes power-related issues like random shutdowns or inability to charge, not localized touchscreen unresponsiveness along one edge.
★ When this WOULD be the correct answer
A user reports that their smartphone randomly shuts down even when the battery indicator shows 30% charge, and the device fails to power on without being plugged in. In that scenario, a failing battery is the most likely cause.
Why candidates choose this
Candidates may associate any hardware malfunction with the battery, especially when troubleshooting unresponsive behavior, due to a lack of understanding of how digitizers and batteries affect device functionality differently.
✗A corrupt operating systemWrong answer — click to see why▾
Why this is wrong here
A corrupt operating system would typically cause system-wide issues like boot loops, app crashes, or full unresponsiveness, not a localized touchscreen failure along one edge.
★ When this WOULD be the correct answer
A corrupt operating system would be correct if the user reports that the smartphone fails to boot, freezes during startup, or experiences persistent app crashes after an update, with no hardware damage or physical symptoms.
Why candidates choose this
Candidates may confuse software corruption with hardware issues, especially if they've experienced OS bugs that affect touch input, but they overlook that localized problems point to digitizer failure.
✗A damaged LCD displayWrong answer — click to see why▾
Why this is wrong here
A damaged LCD display typically causes visual issues like dead pixels, discoloration, or black spots, not unresponsive touch input. The touch functionality is handled by the digitizer, not the LCD.
★ When this WOULD be the correct answer
A damaged LCD display would be correct if the user reported visual anomalies such as lines, flickering, or a black screen, rather than touch unresponsiveness. For example: 'A user reports the screen shows vertical lines and flickering after a drop.'
Why candidates choose this
Candidates may confuse the LCD (display) with the digitizer (touch sensor), assuming any screen issue involves the LCD. They might also think physical damage affects both layers equally.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 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 220-1101 exam.