Final answer:
O-level activities with 6 or less aircraft require a 4B work center.
Step-by-step explanation:
For O-level activities with 6 or less aircraft, a 4B work center is required instead of a 12C work center. The 4B work center is responsible for coordinating and overseeing the maintenance activities for a small number of aircraft. It ensures that the necessary inspections, repairs, and servicing are carried out efficiently and in compliance with regulations.