Auctions (拍卖)are public sales of goods, conducted by an officially approved auctioneer. He asks the crowd assembled in the auction room to make offers, or "bids", for the various items on sale. He encourages buyers to bid higher figures, and finally names the highest bidder as the buyer of goods. This is called "knocking down the goods, for the bidding ends when the auctioneer bangs a small hammer on a table at which he stands, This is often set on a raised platform called a rostrum. The ancient Romans probably invented sales by auction, and the English word comes from the Latin auction, meaning "increase". The Romans usually sold in this way the spoils taken in war; these sales were called "subusta", meaning "under the spear", a spear being stuck in the ground as a signal for a crowd to gather. In the eighteenth and nineteenth centuries goods were often sold by the candle’, a short candle was lit by the auctioneer; and bids could be made while it stayed alight. An auction is usually advertised beforehand with full particulars of the articles to be sold and where and when they can be viewed by possible buyers. If the advertisement cannot give full details, catalogues are printed, and each group of goods to be sold together, called a "lot", is usually given a number. The auctioneer need not begin with lot 1 and continue in numerical order; be may wait until he registers the fact that certain dealers arc in the room and then pro- duce the lots they are likely to be interested in. The auctioneer’s services are paid for in the form of a percentage of the price the goods are sold for. The auctioneer therefore has a direct interest in pushing up the bidding as high as possible. Practicaly all goods whose qualities vary are sold by auction. Among these are coffee, hider, skins, wool, tea, cocoa, furs, spices, fruit and vegetables and wines. Auction sales are also usual for land and property, antique, furniture, pictures, rare books, old china, and similar works of art. The auction-rooms at Christie’s and Sotheby’s in London and New York are world famous.A candle used to bum at auction sales ______. A. because they took place at nightB. as a signal for the crowd togetherC. to limit the time when offers could be madeD. to keep the auctioneer warm