What must be prominently displayed according to FTC regulations?

The correct choice involves the FTC Buyer's Guide, which is mandated by federal regulations to be displayed prominently by dealers in the sale of used vehicles. This guide serves to inform potential buyers about the vehicle's condition, including any warranty information and their rights, ensuring transparency in the sale process.

The presence of the FTC Buyer's Guide is crucial because it provides essential information such as whether the vehicle is being sold "as is" or with a warranty, which directly affects the buyer's rights post-sale. This regulation aims to protect consumers from deceptive practices and ensures they have access to vital information before making a purchasing decision.

While other options may involve important documents relevant to vehicle transactions, they do not have the same federal regulatory requirement for prominent display as the FTC Buyer's Guide does. Therefore, understanding the significance of the FTC Buyer's Guide helps in complying with fair trade practices and promoting consumer awareness in the automotive sales industry.