阅读下面短文,回答下列五道题桥是种固定建筑物,一经造成,便屹立大地,可以千载不移,把它当作地面标志,应当是再准确不过的。《史记·苏秦列传》里有段故事:“尾生(人名)与女子期于梁下,女子不来,水至不去,抱柱而死。”他们所以约定在桥下相会,就因为桥是不会动的,但是,这里所谓不动,是指大动而言,至于小动、微动,它却和万物一样,是持续不断、分秒不停的。车在桥上过,它的重量就使桥身变形,从平直的桥身变为弯曲的桥身,就同人坐在板凳上,把板凳坐弯一样。板凳的腿,因为板的压迫,也要变形,如果这腿是有弹簧的,就可看出,这腿是被压短了。桥身的两头是桥墩,桥上不断行车,桥墩就像凳腿一样,也要被压短而变形。把板凳放到泥土上,坐上人,板凳腿就把人的重量传到泥土中,使泥土发生变形。桥墩也同样使下面的基础变形。桥身的变形表示桥上的重量传递给桥墩了,桥墩的变形表示桥身上的重量传递给基础了,基础的变形表示桥墩上的重量传递给桥下的土地了,桥上的重量终为地下的抵抗所平衡。物体所以能变形,是由于内部分子的位置有变动,也就是由于分子的运动。车在桥上高速行驶时,使桥梁整体发生震动。此外,桥还受气候变化的侵袭。在狂风暴雨中,桥是要摆动或扭动的;就是在冷暖不均,温度有升降时,桥也要伸缩,形成蠕动。桥墩在水中,经常受水流的压迫和风浪的打击,就有摇动、转动和滑动的倾向而在地基中发生移动。此外,遇到地震,桥还会受到水下方向和由下而上的推动。所有以上种种的动而引起的桥的变形,加上桥上重量和桥本身重量所引起的变形,构成全桥各部的总变形。任何一点的变形,都是那里的分子运动的综合表现。桥是固定建筑物,所谓固定就是不在空间有走动,不像车船行走。但是,天地间没有完全固定的东西,桥的平衡只能是瞬间现象,它仍是桥的运动的一种特殊状态。桥的运动是桥的存在形式。 下列对本文中心的归纳,正确的一项是()。
A. 桥在重力作用和各种外力的影响下会发生变形
B. 桥无时无刻不在运动,桥的运动就是桥的存在形式
C. 桥的平衡是桥的运动的一种特殊状态,是瞬间现象
D. 桥任何一点的变形,都是那里的分子运动的综合表现
Auctions 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 the 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 auctio, meaning "increase". The Romans usually sold in this way the spoils taken in war; these sales were called sub basra, meaning "under the spear", a spear being stuck in the ground as a signal for a crowd to gather. In England 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. Practically all goods whose qualities vary are sold by auction. Among these are coffee, hides, 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. An auction is usually advertised beforehand with full particulars of the articles to be sold and where and when they can be viewed by prospective 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, he may wait until he registers the fact that certain dealers are in the room and then produce 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. The auctioneer must know fairly accurately the current market values of the goods he is selling, and he should be acquainted with regular buyers of such goods. He will not waste time by starting the bidding too low. He will also play on the rivalries among his buyers and succeed in getting a high price by encouraging two business competitors to bid against each other. It is largely on his advice that a seller will fix a "reserve" price, that is, a price below which the goods cannot be sold. Even the best auctioneers, however, find it difficult to stop a "knockout", whereby dealers illegally arrange beforehand not to bid against each other, but nominate one of themselves as the only bidder, in the hope of buying goods at extremely low prices. If such a "knockout" comes off, the real auction sale takes place privately afterwards among the dealers. An auction catalogue gives prospective buyers ______.
A. the current market values of the goods
B. details of the goods to be sold
C. the order in which goods must be sold
D. free admission to the auction sale