The correct answer is that the IAM policy lacks the `s3:ListBucket` permission. This is because the SageMaker Processing job’s Access Denied error when listing objects in S3 stems from the `ListObjectsV2` API call, which requires the `s3:ListBucket` action at the bucket level—separate from object-level permissions like `s3:GetObject` or `s3:PutObject`. On the AWS Certified Machine Learning Engineer Associate MLA-C01 exam, this scenario tests your understanding of S3 IAM policy granularity, where a common trap is assuming `s3:*` or object-level actions cover bucket listing. Remember that `s3:ListBucket` is a bucket-scoped permission, not an object-scoped one, so it must be explicitly allowed in the policy’s Resource element pointing to the bucket ARN. A useful memory tip: “List the bucket, then get the object—two separate permissions, two separate API calls.”
MLA-C01 Data Preparation for Machine Learning Practice Question
This MLA-C01 practice question tests your understanding of data preparation for machine learning. 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.
Exhibit
Refer to the exhibit. A data scientist is trying to run a SageMaker Processing job that reads data from an S3 bucket. The IAM role attached to the processing job has the following policy:
```json
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:GetObject",
"Resource": "arn:aws:s3:::my-bucket/*"
}
]
}
```
The job fails with an error: "Access Denied" when trying to list objects. What is the root cause?
A SageMaker Processing job fails with 'Access Denied' when listing objects in an S3 bucket, despite the IAM policy shown in the exhibit. 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.
Refer to the exhibit. A data scientist is trying to run a SageMaker Processing job that reads data from an S3 bucket. The IAM role attached to the processing job has the following policy:
```json
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:GetObject",
"Resource": "arn:aws:s3:::my-bucket/*"
}
]
}
```
The job fails with an error: "Access Denied" when trying to list objects. What is the root cause?
A
The policy lacks `s3:ListBucket` permission.
ListBucket is required to list objects; GetObject alone is insufficient.
B
The role does not have a trust relationship with SageMaker.
Why wrong: Trust relationship issues cause role assumption failures, not listing errors.
C
The bucket policy denies the access.
Why wrong: While possible, the direct cause is the missing ListBucket permission in the role.
D
The bucket is in a different region.
Why wrong: Region mismatch results in a different error message.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy lacks `s3:ListBucket` permission.
The error 'Access Denied' when listing objects in an S3 bucket indicates that the IAM role used by the SageMaker Processing job lacks the `s3:ListBucket` permission. This permission is required for the `ListObjectsV2` API call, which is necessary to enumerate objects in the bucket. Even if the role has `s3:GetObject` and `s3:PutObject` permissions, without `s3:ListBucket`, the job cannot list the bucket contents and will fail with an access denied error.
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 policy lacks `s3:ListBucket` permission.
Why this is correct
ListBucket is required to list objects; GetObject alone is insufficient.
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 role does not have a trust relationship with SageMaker.
Why it's wrong here
Trust relationship issues cause role assumption failures, not listing errors.
✗
The bucket policy denies the access.
Why it's wrong here
While possible, the direct cause is the missing ListBucket permission in the role.
✗
The bucket is in a different region.
Why it's wrong here
Region mismatch results in a different error message.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the distinction between `s3:ListBucket` (required for listing objects) and `s3:GetObject` (required for reading objects), leading candidates to incorrectly assume that having `s3:GetObject` alone is sufficient for all S3 read operations.
Detailed technical explanation
How to think about this question
The `s3:ListBucket` permission controls the `ListObjectsV2` and `ListObjects` API operations, which are required for any operation that enumerates bucket contents, such as reading a manifest file or iterating over input data. Without this permission, the SageMaker Processing job's `s3fs` or `boto3` client will fail at the listing step, even if the role has `s3:GetObject` for individual objects. In real-world scenarios, this often occurs when using SageMaker's `ProcessingInput` with a manifest file or when the job needs to discover input files dynamically.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Data Preparation for Machine Learning — This question tests Data Preparation for Machine Learning — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The policy lacks `s3:ListBucket` permission. — The error 'Access Denied' when listing objects in an S3 bucket indicates that the IAM role used by the SageMaker Processing job lacks the `s3:ListBucket` permission. This permission is required for the `ListObjectsV2` API call, which is necessary to enumerate objects in the bucket. Even if the role has `s3:GetObject` and `s3:PutObject` permissions, without `s3:ListBucket`, the job cannot list the bucket contents and will fail with an access denied error.
What should I do if I get this MLA-C01 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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Question Discussion
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