The correct answer is B) American Bureau of Shipping. The American Bureau of Shipping (ABS) is the organization responsible for certifying the safe working load (SWL) of cargo booms on vessels. ABS is a classification society that sets and maintains standards for the design, construction, and operation of marine vessels. As part of their role, ABS inspects and approves the safe working loads for all equipment on board, including cargo booms, to ensure the vessel's safety and seaworthiness. The U.S. Coast Guard (option A) does not directly certify the SWL of cargo booms, but they do enforce regulations that require vessels to have their cargo gear certified by a recognized organization like ABS. The Society of Naval Architects and Marine Engineers (option C) and the Ship's Master (option D) do not have the authority to officially certify the SWL of cargo booms.