Quick Answer
The answer is `aws_instance.example[2].id` because Terraform uses zero-based indexing with the `count` meta-argument, meaning the first instance is at index 0, the second at index 1, and the third at index 2. When you need to reference a specific instance created by `count`, you access it using bracket notation with the resource type and local name followed by the index, then the attribute—so `aws_instance.example[2].id` correctly retrieves the ID of the third EC2 instance. On the HashiCorp Terraform Associate TF-003 exam, this question tests your understanding of how `count` creates a list of resources and how to index into that list, a common scenario when managing multiple similar resources. A frequent trap is forgetting that indices start at zero, leading candidates to mistakenly choose index 3 for the third instance, which actually refers to the fourth. Remember the memory tip: "Count starts at zero, so third is number two."
This TF-003 practice question tests your understanding of understand iac concepts. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 team uses Terraform to manage multiple AWS EC2 instances with a 'count' meta-argument. They need to reference the ID of the third instance in another resource's configuration. Which expression should they use?
aws_instance.example[1].id
Why wrong: Index 1 refers to the second instance.
aws_instance.example[2].id
Index 2 is the third instance (zero-based).
element(aws_instance.example.*.id, 3)
Why wrong: element with index 3 returns the fourth instance.
aws_instance.example[3].id
Why wrong: Index 3 refers to the fourth instance (zero-based).
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
aws_instance.example[2].id
Option D is correct because indices are zero-based, so 'aws_instance.example[2]' refers to the third instance. Option A (index 3) is the fourth. Option B (index 1) is the second. Option C uses 'element' with index 3, also the fourth.
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.
aws_instance.example[1].id
Why it's wrong here
Index 1 refers to the second instance.
aws_instance.example[2].id
Why this is correct
Index 2 is the third instance (zero-based).
Related concept
Read the scenario before looking for a memorised answer.
element(aws_instance.example.*.id, 3)
Why it's wrong here
element with index 3 returns the fourth instance.
aws_instance.example[3].id
Why it's wrong here
Index 3 refers to the fourth instance (zero-based).
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 TF-003 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 TF-003 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
Understand IaC concepts — This question tests Understand IaC concepts — Read the scenario before looking for a memorised answer..
The correct answer is: aws_instance.example[2].id — Option D is correct because indices are zero-based, so 'aws_instance.example[2]' refers to the third instance. Option A (index 3) is the fourth. Option B (index 1) is the second. Option C uses 'element' with index 3, also the fourth.
Identify which TF-003 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
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