Final answer:
Congressional hearings and investigations are the most visible indication of political oversight of the bureaucracy.
Step-by-step explanation:
The most visible indication of political oversight of the bureaucracy is congressional hearings and investigations. Congress holds regular hearings to question the leaders of bureaucratic agencies, particularly when there are concerns or issues that need to be addressed. These hearings provide a platform for legislators to exercise their oversight powers and hold the bureaucracy accountable for their actions.