The correct answer is C. Transpose. According to CompTIA DataSys+ objectives, spreadsheet tools are often used alongside databases for reporting, analysis, and data validation. The Transpose function is specifically designed to switch data orientation, converting rows into columns or columns into rows. This makes it the most efficient and accurate choice when an analyst needs to quickly reformat data for analysis or reporting purposes.

In practical scenarios, error reports or exported datasets may not always align with the structure required for analytical tools or pivot-style analysis. Transpose allows analysts to reshape the data without rewriting formulas or manually re-entering values. DataSys+ highlights the importance of understanding basic data manipulation techniques in spreadsheets, especially when working with imported or exported database data.

Option A, Concat, is used to combine text from multiple cells into a single cell and does not change the orientation of data. Option B, VLOOKUP, is a lookup function used to retrieve matching values from a table based on a key; it does not modify how data is arranged. Option D, Clean, is used to remove non-printable characters from text and is helpful for data cleansing, not restructuring.

Transpose is particularly useful because it preserves the original data values while changing their layout, reducing the risk of data corruption or misinterpretation. CompTIA DataSys+ emphasizes efficiency and accuracy in data handling, especially when analysts must respond quickly to reporting or troubleshooting needs.

By using Transpose, the analyst can immediately align the dataset with the required analytical format, saving time and ensuring consistency. Therefore, the spreadsheet function that best meets the requirement of switching rows to columns is Transpose, making option C the correct and fully verified answer.