- A
Connect to folder, replace nulls in each file, combine files, remove duplicates, set data types.
Why wrong: Replacing nulls in each file before combining is inefficient because you would need to apply the same step to each file individually; it's better to combine first and then transform.
- B
Connect to folder, combine files, set data types, replace nulls, remove duplicates.
Why wrong: Setting data types before replacing nulls might cause errors if nulls are in numeric columns; it's better to replace nulls first.
- C
Connect to folder, combine files, remove duplicates, replace nulls, set data types.
Why wrong: Removing duplicates before replacing nulls may not clean data effectively; also, null replacement should come before type setting.
- D
Connect to folder, combine files, replace nulls, remove duplicates, set data types.
This order ensures nulls are handled before deduplication, and data types are set last to avoid conversion issues.
Quick Answer
The correct sequence is to connect to the folder, combine the CSV files, replace nulls, remove duplicates, then set data types. This order is essential because Power Query processes steps sequentially; replacing nulls in ScrapUnits with 0 before removing duplicates ensures that rows with missing values are preserved and fixed, rather than being discarded prematurely. On the Microsoft Power BI Data Analyst PL-300 exam, this question tests your understanding of the M-shaped data transformation workflow, where combining files from a folder is the foundational step, followed by cleaning—a common trap is to set data types too early, which can break transformations on null values. A reliable memory tip is the acronym C-R-R-D-T: Combine, Replace, Remove, Data Types—think of it as “Clean, then Type,” ensuring you fix missing values and duplicates before locking in column formats.
PL-300 Prepare the data Practice Question
This PL-300 practice question tests your understanding of prepare the data. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
You are a business analyst at a manufacturing company. You receive weekly CSV files from different plants. Each file contains columns: PlantID, Date, ProductID, UnitsProduced, and ScrapUnits. However, the files sometimes have missing values in the ScrapUnits column, and occasionally there are duplicate rows (same PlantID, Date, ProductID). You need to prepare a clean dataset for reporting. The requirements are: 1. Combine all CSV files from a folder into a single table. 2. Replace null values in ScrapUnits with 0. 3. Remove duplicate rows based on PlantID, Date, and ProductID, keeping the first occurrence. 4. Ensure the data types are appropriate (e.g., Date as date, UnitsProduced as whole number).
Which sequence of Power Query steps should you use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Connect to folder, combine files, replace nulls, remove duplicates, set data types.
Option C is correct because the logical order is: connect to folder, combine files, then clean data (replace nulls, remove duplicates) and set data types. Option A is incorrect because setting data types before cleaning can cause errors. Option B is incorrect because removing duplicates before replacing nulls may remove rows that could be fixed. Option D is incorrect because removing duplicates before combining files would apply to each file individually, not across files.
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.
- ✗
Connect to folder, replace nulls in each file, combine files, remove duplicates, set data types.
Why it's wrong here
Replacing nulls in each file before combining is inefficient because you would need to apply the same step to each file individually; it's better to combine first and then transform.
- ✗
Connect to folder, combine files, set data types, replace nulls, remove duplicates.
Why it's wrong here
Setting data types before replacing nulls might cause errors if nulls are in numeric columns; it's better to replace nulls first.
- ✗
Connect to folder, combine files, remove duplicates, replace nulls, set data types.
Why it's wrong here
Removing duplicates before replacing nulls may not clean data effectively; also, null replacement should come before type setting.
- ✓
Connect to folder, combine files, replace nulls, remove duplicates, set data types.
Why this is correct
This order ensures nulls are handled before deduplication, and data types are set last to avoid conversion issues.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which PL-300 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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Prepare the data — study guide chapter
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FAQ
Questions learners often ask
What does this PL-300 question test?
Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Connect to folder, combine files, replace nulls, remove duplicates, set data types. — Option C is correct because the logical order is: connect to folder, combine files, then clean data (replace nulls, remove duplicates) and set data types. Option A is incorrect because setting data types before cleaning can cause errors. Option B is incorrect because removing duplicates before replacing nulls may remove rows that could be fixed. Option D is incorrect because removing duplicates before combining files would apply to each file individually, not across files.
What should I do if I get this PL-300 question wrong?
Identify which PL-300 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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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Last reviewed: Jun 21, 2026
This PL-300 practice question is part of Courseiva's free Microsoft 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 PL-300 exam.
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