Which of the following can be a cause for suspension or revocation of an auctioneer's license?

Not disclosing a buyer's premium is a valid cause for suspension or revocation of an auctioneer's license because it directly affects the transparency and integrity of the auction process. Auctioneers have a legal and ethical obligation to disclose all fees that will be charged to buyers, including any buyer's premium. This ensures that buyers are aware of the total cost they will incur when participating in the auction. Failure to disclose such information can mislead buyers, resulting in unfair auction practices, which regulatory authorities aim to prevent. Maintaining transparency is essential for building trust in the auction process, and thus, such a violation can lead to disciplinary actions against the auctioneer.

In contrast, failing to provide entertainment, conducting a charity auction, or hosting auctions in different states do not typically constitute violations that could lead to license suspension or revocation, as these activities do not directly undermine the principles of honesty and fairness that govern auctioneering practices.