Final Answer:
The mandatory oversight procedure in the GPC program, specified by TO2 EO2, involves validating the closure of all data mining cases and assessing key internal controls related to purchasing and management.
Step-by-step explanation:
In the Government Purchase Card (GPC) program, TO2 EO2 refers to a specific oversight procedure. This procedure is designed to ensure compliance and effectiveness in the program. The validation of data mining case closures is crucial for maintaining the integrity of the program, as it confirms that any identified issues or discrepancies have been appropriately addressed. Additionally, the assessment of key internal controls related to purchasing and management helps identify and mitigate potential risks in these areas. Overall, TO2 EO2 contributes to the overall accountability and efficiency of the GPC program. Therefore, the correct answer is option D: "Validate data mining cases closure and assess key purchasing and management controls."