题型:填空题 .To help today’s customers make a choice, a company in New York _____a video trolley — a supermarket trolley with a video screen to display advertisement and price information. A.has inventedB.had inventedC.inventsD.is inventing 查看答案
题型:填空题 一商店以每3盘16元的价格购进一批光盘,又从另外一处以每4盘21元的价格购进比前一批数量加倍的光盘,若以每3盘y元的价格全部卖掉,可得到所投资的x倍的收益,则y与x之间的函数关系是()。A.AB.BC.CD.DE.E 查看答案