The answer is the s3:ExistingObjectTag condition key on the ListBucket action. This condition requires every object in the bucket to possess the tag 'data-type'='training' for the list operation to succeed, and if any object lacks that tag, the AWS CLI command fails with an access denied error. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding that ListBucket operates at the bucket level, yet the ExistingObjectTag condition is evaluated against each object's metadata, creating a common trap where you might overlook that a single untagged object blocks the entire listing. A key memory tip is to remember that ListBucket with ExistingObjectTag is like a bouncer checking every guest's ID before letting anyone into the party—if one guest lacks the right tag, nobody gets in.
MLS-C01 Exploratory Data Analysis Practice Question
This MLS-C01 practice question tests your understanding of exploratory data analysis. 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 data scientist is trying to list objects in an S3 bucket named 'my-bucket' using the AWS CLI command: `aws s3 ls s3://my-bucket/`. The command fails with an access denied error. The IAM policy attached to the scientist's role is shown in the exhibit. What is the most likely cause of the failure?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The condition on the ListBucket action requires all objects to have the tag 'data-type'='training', which may not be satisfied.
Option B is correct because the ListBucket action is conditioned on the s3:ExistingObjectTag/data-type condition, which requires that all objects in the bucket have the tag 'data-type' set to 'training'. However, the ListBucket action applies to the bucket, not individual objects, and the condition might not be evaluated correctly, but more importantly, the condition on ListBucket is unusual; typically conditions on ListBucket should be avoided or use different keys. However, the most direct issue is that the condition must be satisfied for the request, and if the bucket has objects without that tag, the ListBucket action is denied. Option A is wrong because the policy includes s3:ListBucket on the bucket ARN. Option C is wrong because the condition uses StringEquals, not a request parameter. Option D is wrong because the bucket exists and the user has permission if the condition is met.
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 condition on the ListBucket action requires all objects to have the tag 'data-type'='training', which may not be satisfied.
Why this is correct
The condition on ListBucket is problematic and may cause denial.
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 IAM policy does not include the s3:ListBucket action.
Why it's wrong here
The policy does include ListBucket.
✗
The policy does not grant access to the bucket because it uses 'my-bucket' instead of the full ARN.
Why it's wrong here
The ARN is correctly specified.
✗
The condition should use 'StringLike' instead of 'StringEquals'.
Why it's wrong here
StringEquals is correct for exact match.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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
How to think about this question
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.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which MLS-C01 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.
Exploratory Data Analysis — This question tests Exploratory Data Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The condition on the ListBucket action requires all objects to have the tag 'data-type'='training', which may not be satisfied. — Option B is correct because the ListBucket action is conditioned on the s3:ExistingObjectTag/data-type condition, which requires that all objects in the bucket have the tag 'data-type' set to 'training'. However, the ListBucket action applies to the bucket, not individual objects, and the condition might not be evaluated correctly, but more importantly, the condition on ListBucket is unusual; typically conditions on ListBucket should be avoided or use different keys. However, the most direct issue is that the condition must be satisfied for the request, and if the bucket has objects without that tag, the ListBucket action is denied. Option A is wrong because the policy includes s3:ListBucket on the bucket ARN. Option C is wrong because the condition uses StringEquals, not a request parameter. Option D is wrong because the bucket exists and the user has permission if the condition is met.
What should I do if I get this MLS-C01 question wrong?
Identify which MLS-C01 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.
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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Question Discussion
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