Final answer:
The right file format for creating PivotTables in Tableau with an Excel file is XLSX, but if 'cs file' means a CSV file, then CSV is also suitable for data import into Tableau.
Step-by-step explanation:
In a case study involving creating PivotTables in Tableau, the file format designed to work with the Excel file titled "cs file" is likely a typographical error and supposed to be "csv file". The correct file format to use with Excel files for data import into Tableau is b. XLSX. However, if "cs file" refers to a comma-separated values file, the answer would be a. CSV. CSV files are plain text files with values separated by commas, and they are often used for transferring tabular data between different programs, such as from Excel to Tableau.