What is one common feature of online auctions?

One common feature of online auctions is that bidders participate remotely through a digital platform. This allows individuals from various locations to access the auction, view items, and place bids without the need to be physically present at an auction site. The convenience of online platforms is a significant advantage and attracts a broader audience, as it eliminates geographic barriers and enables participation at any time during the auction period. Unlike traditional auctions, where physical presence is often required, online auctions maximize accessibility and flexibility for bidders.

In the context of the other options, the notion that all items must be delivered on the day of the auction does not align with typical online auction practices, where delivery timelines can vary. Physical presence to bid contradicts the very nature of online bidding, which is designed for remote participation. Additionally, the statement regarding reserve prices is inaccurate as many online auctions can and do feature reserve prices, which set a minimum price the item must reach for the bid to be accepted.