The answer is that the IAM role lacks the required s3:GetObject permission on the S3 bucket or its objects. This is because when you create a SageMaker training job, the service assumes the specified IAM role to access your training data; if that role does not include a policy granting read access to the S3 bucket listed in the command, the job immediately fails with the "Unable to read data" error. On the AWS Certified Machine Learning Specialty MLS-C01 exam, this scenario tests your understanding of how SageMaker’s execution role interacts with S3 permissions—a common trap is assuming the error is due to bucket region mismatch or network issues, when in fact the IAM policy is missing. Remember the mnemonic: "Role reads, role writes—if S3 fails, check the IAM rights."
MLS-C01 Modeling Practice Question
This MLS-C01 practice question tests your understanding of modeling. 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.
Refer to the exhibit. A data scientist runs the above CLI command to create a SageMaker training job. The job fails with an error 'Unable to read data from s3://bucket/train/'. 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.
Why wrong: Image accessibility would cause a different error (e.g., 'Unable to pull image').
B
The instance type does not support the required memory
Why wrong: Instance memory would cause an out-of-memory error, not a data read error.
C
The IAM role does not have permissions to read from the S3 bucket
The role must have s3:GetObject permission for the training data.
D
The training job is in a different region than the S3 bucket
Why wrong: S3 is region-agnostic for access, but cross-region access requires explicit permission; however, the error message suggests a permission issue.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The IAM role does not have permissions to read from the S3 bucket
The error 'Unable to read data from s3://bucket/train/' indicates that the SageMaker training job cannot access the S3 input data. The most common cause is that the IAM role specified in the command does not have the necessary s3:GetObject permission on the S3 bucket or objects. SageMaker uses the IAM role to assume permissions for reading training data, and without proper S3 read access, the job fails at the data loading stage.
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 training image is not accessible
Why it's wrong here
Image accessibility would cause a different error (e.g., 'Unable to pull image').
✗
The instance type does not support the required memory
Why it's wrong here
Instance memory would cause an out-of-memory error, not a data read error.
✓
The IAM role does not have permissions to read from the S3 bucket
Why this is correct
The role must have s3:GetObject permission for the training data.
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 training job is in a different region than the S3 bucket
Why it's wrong here
S3 is region-agnostic for access, but cross-region access requires explicit permission; however, the error message suggests a permission issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the error message with a network or region issue, but the 'Unable to read data' error is almost always an IAM permissions problem, not a connectivity or resource constraint issue.
Detailed technical explanation
How to think about this question
SageMaker training jobs use the IAM execution role to sign requests to S3 via AWS Signature Version 4. The role must have an attached policy allowing s3:GetObject on the bucket/prefix, and if the bucket uses a bucket policy, it must also grant access to the role. A common subtle issue is that the role may have S3 read permissions but the bucket policy explicitly denies access from the SageMaker service principal, causing a silent failure. Additionally, if the S3 bucket uses SSE-KMS encryption, the role also needs kms:Decrypt permissions on the KMS key.
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.
Modeling — This question tests Modeling — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The IAM role does not have permissions to read from the S3 bucket — The error 'Unable to read data from s3://bucket/train/' indicates that the SageMaker training job cannot access the S3 input data. The most common cause is that the IAM role specified in the command does not have the necessary s3:GetObject permission on the S3 bucket or objects. SageMaker uses the IAM role to assume permissions for reading training data, and without proper S3 read access, the job fails at the data loading stage.
What should I do if I get this MLS-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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A data scientist is trying to create a SageMaker training job but receives an access denied error. The IAM policy attached to the role is shown in the exhibit. What is the most likely cause of the error?
medium
✓ A.The policy does not allow s3:PutObject for the output location
B.The policy does not allow sagemaker:CreateTrainingJob
C.The policy has an explicit deny on s3:PutObject
D.The policy does not allow s3:GetObject on the output bucket
Why A: Option B is correct because the policy lacks permissions to write output to S3. The s3:PutObject action is missing. Option A is wrong because the policy allows s3:GetObject. Option C is wrong because sagemaker:CreateTrainingJob is allowed. Option D is wrong because there is no condition denying writes.
Last reviewed: Jun 24, 2026
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This MLS-C01 practice question is part of Courseiva's free Amazon Web Services 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 MLS-C01 exam.
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