Final answer:
The Campaign Budget Usage report is used to identify when a campaign has overspent by comparing allocated budgets to actual spending. The option (D) is correct.
Step-by-step explanation:
To identify when a campaign has overspent, you would use the Campaign Budget Usage report. This report allows you to track the budget that has been allocated to a campaign and compare it to the actual spend. If the actual spending exceeds the budgeted amount, it indicates that the campaign has overspent.
Correctly monitoring the Campaign Budget Usage report is essential for maintaining control over marketing expenditures and ensuring that each campaign stays within its financial parameters. Therefore, option (D) is correct.