What is an auctioneer's duty regarding reserve prices?

An auctioneer's duty regarding reserve prices is to ensure transparency and fairness in the auction process. This is crucial because a reserve price is the minimum price that a seller is willing to accept for an item. If there is a reserve price, it impacts the bidders' decision-making process significantly.

Informing bidders that a reserve price exists helps establish trust and allows participants to make informed offers. It ensures that bidders understand that the item may not be sold unless the bidding meets or exceeds the specified amount. This transparency is a vital part of maintaining the integrity of the auction and protecting both the interests of the seller and the rights of the bidders.

In contrast, the other choices suggest either complete opacity regarding the reserve price or imply that it is acceptable to change or lower the reserve at whim, which undermines the fairness and predictability that bidders expect in an auction setting.