Quick Answer
The answer is def456 because a null pointer bug must have been introduced in a commit that occurred before the fix commit, and after the initial stable commit. In Git history, when a bug is fixed in commit 789ghi, the defect was likely injected in the most recent prior commit that changed the code—def456, which added a new feature. This tests your ability to trace a regression backward through a commit log, a common skill for the CompTIA ITF+ FC0-U61 exam’s troubleshooting and software development concepts. A frequent trap is to pick the fix commit itself, but the fix resolves the bug, not introduces it. Remember: the commit that introduces a bug is always the one just before the fix, not the fix itself—think “before the fix, not the fix.”
This FC0-U61 practice question tests your understanding of software development concepts. 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 developer sees the above output. After a recent commit, the application crashed due to a null pointer. Which commit likely introduced the null pointer issue?
def456
The null pointer bug likely originated in the new feature commit def456.
abc123
Why wrong: abc123 is a later fix, not the introducer.
012jkl
Why wrong: Initial commit likely did not contain the bug.
789ghi
Why wrong: 789ghi is the fix commit.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
def456
The correct answer is C: def456. The null pointer was fixed in 789ghi, so the bug was introduced before that. The initial commit (D) likely didn't have the bug. The bug fix (A) fixes it. The fix commit shows 'Fixed bug', but the null pointer fix is 789ghi. So the commit that introduced it is def456. Wait: The exhibit shows: abc123 fixed bug, def456 added feature, 789ghi fixed null pointer, 012jkl initial. So the null pointer was fixed in 789ghi. It was introduced in the commit before that? Usually the bug is introduced in a prior commit. The question asks: 'After a recent commit, the application crashed due to a null pointer.' Which commit likely introduced the null pointer? Since it was fixed in 789ghi, it was likely introduced in def456 (the addition of new feature). So correct answer is B: def456. But options: A abc123, B def456, C 789ghi, D 012jkl. Correct is B.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
def456
Why this is correct
The null pointer bug likely originated in the new feature commit def456.
Related concept
Read the scenario before looking for a memorised answer.
abc123
Why it's wrong here
abc123 is a later fix, not the introducer.
012jkl
Why it's wrong here
Initial commit likely did not contain the bug.
789ghi
Why it's wrong here
789ghi is the fix commit.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the FC0-U61 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
Identify which FC0-U61 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Software Development Concepts — This question tests Software Development Concepts — Read the scenario before looking for a memorised answer..
The correct answer is: def456 — The correct answer is C: def456. The null pointer was fixed in 789ghi, so the bug was introduced before that. The initial commit (D) likely didn't have the bug. The bug fix (A) fixes it. The fix commit shows 'Fixed bug', but the null pointer fix is 789ghi. So the commit that introduced it is def456. Wait: The exhibit shows: abc123 fixed bug, def456 added feature, 789ghi fixed null pointer, 012jkl initial. So the null pointer was fixed in 789ghi. It was introduced in the commit before that? Usually the bug is introduced in a prior commit. The question asks: 'After a recent commit, the application crashed due to a null pointer.' Which commit likely introduced the null pointer? Since it was fixed in 789ghi, it was likely introduced in def456 (the addition of new feature). So correct answer is B: def456. But options: A abc123, B def456, C 789ghi, D 012jkl. Correct is B.
Identify which FC0-U61 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This FC0-U61 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 FC0-U61 exam.
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