For a list report that includes columns for purchase requests and regional cost centers, and with a requirement to show the total number of purchase requests for each regional cost center, the correct approach is to summarize the relevant data in a way that aligns with the manager's needs.

C. Summarize the purchase requests column by count: This configuration aggregates the purchase requests data, providing a count of purchase requests per cost center. It effectively meets the manager's requirement by offering a clear and concise summary of the total number of purchase requests for each regional cost center, facilitating easy analysis and decision-making.

Using the purchase requests column to group the cost centers (A) might organize the data differently than required, focusing on purchase requests rather than summarizing them by count for each cost center. Filtering the results to include only cost center and purchase requests (B) simplifies the report but does not aggregate the data as