例五：
Directions:Readthefollowingandchoosethetitlethatbestexpressestheideas ofthepassage.
Thereisasimpleeconomicprincipleusedtodetermineprices.Itiscalledthelaw
ofsupplyanddemand.Supplymeanstheamountof,oraccessto,certaingoods.Dema ndrepresentsthenumberofpeoplewhowantthosegoods.Iftherearemoregoodstha  nwanted,thepriceofthemfalls.Ontheotherhand,ifthedemandforthosegoodsis
muchgreaterthanthesupply,thenthepricerises.Ofcourse,manufacturerspref ertosellmoregoodsatincreasedprices.
(A)EconomicPrinciples
(B)LawofSupplyandDemand  (C)MoreGoods,LowerPrices
(D)FewerGoods,HigherPrices
该问题中，(A)泛指经济规律，面过宽；(C)和(D)只是供需规则的二个单独的方面 不能包含全部，面太窄。正确的答案是(B),  因为这正是该短文自始至终谈论的 主题。