The correct answer is A) classification society. The classification society is the organization responsible for certifying the safe working load of cargo cranes and other equipment on a vessel. Classification societies, such as the American Bureau of Shipping (ABS) or Lloyd's Register, establish and enforce standards for the design, construction, and maintenance of ships to ensure their safety and seaworthiness. The U.S. Coast Guard (option B) is responsible for enforcing regulations and issuing licenses, but does not directly certify the safe working load of cargo cranes. The National Cargo Bureau (option C) is an independent organization that inspects and certifies the loading and stowage of cargo, but does not certify the cargo handling equipment itself.