The correct answer is A) hatches, doors, and oar ports should be closed. When operating the air supply system in a covered lifeboat, the hatches, doors, and oar ports should be closed to maintain the air supply and ensure the occupants receive adequate ventilation. This is a safety requirement specified in the regulations governing the operation of covered lifeboats. Keeping these openings closed helps prevent the escape of the limited air supply, which is crucial for the survival of the occupants until they can be rescued. The other options are incorrect because they do not directly relate to the proper operation of the air supply system. Shutting off the engine (B) or the fuel supply valve (D) would not affect the air supply, and closing the air cylinder shut-off valve (C) would cut off the air supply, which is the opposite of the correct action.