sthan50%mon.Example2ThegraphshowstheincreasingtrendofenergyconsumptionforUS,Chinaandworldfrom1990to2020.Example3Example4ThefiguresprovidedinthegraphshowstheautosalesofChinaduringtheperiodof2000to2010.Theautosalesincreasedgraduallyfrom2.1millionunitsin2000to9.38millionunitsin2008.In2009,theautosalesrosedramaticallyto13.65millionunits.Accordingtothistrend,thesalesareexpectedtoreach20millionunitsby2010.Example5ThisgraphshowsthetrendofChinesetouristsflockabroadduringtheperiodof1993and2009.Bytheendof2000,theoutboundpopulationincreasedgraduallyto10million.From2000to2003,internationaloutboundtripsroserapidlyto20million.Until2009,theincreasingtrendremained.Chinesetouristsflockreachedthepeakatnearly50millionin2009.Threereasons,Ifirmlybelieve,ountforthisphenomenon.First,money.Second,studentsExample6