Barry collects antique watches and has decided to sell a few of them on eBay. Some of the watches he wants to sell are rare and very valuable. What condition is necessary for an exchange to occur between Barry and a buyer?

a. His watch should have a certificate of authenticity. b. The opening bid must be lower than other watches being sold on the site. c. Buyers must provide payment before the item is shipped. d. Delivery must take place within 2 days of the purchase. e. Potential buyers must be able to see the watch and understand its qualities.