Final answer:
The Occupational Safety and Health Administration (OSHA) requires immediate action when biohazard sharps containers are not maintained according to standards.
Step-by-step explanation:
The regulatory agency that requires immediate action when a medical facility is not maintaining biohazard sharps containers according to the standards, especially when medical staff continue to add needles after the containers are full, is the Occupational Safety and Health Administration (OSHA). OSHA is the federal agency responsible for ensuring safe and healthy working conditions, which includes the proper handling and disposal of sharps to protect healthcare workers and others from potential exposure to bloodborne pathogens and other infectious materials. The correct answer to the question of which regulatory agency would require immediate action in such a scenario is D.) Occupational Safety and Health Administration.