燃料成分分析常用四种分析基准，各基准下，燃料成分百分比不相同的原因是因为（）。
A、燃料中各成分的绝对含量是变化的D
暂无解析
你完全不用刻意去想气质这件事。因为气质就是你自己，你所经历，你所学，你所想的。它就在那里，你想也没有用。
Intheearlieststagesofman'sdevelopmenthehadnomoreneedofmoneythananimalshave.Hewascontentwithverysimpleformsofshelter,madehisownroughtoolsandweaponsandcouldprovidefoodandclothingforhimselfandhisfamilyfromnaturalmaterialsaroundhim.Ashebecamemorecivilized,however,hebegantowantbettershelter,moreefficienttoolsandweapons,andmorecomfortableandmorelastingclothingthancouldbeprovidedbyhisownneighborhoodorbytheworkofhisownunskilledhands.Forthesethingshehadtoturntotheskilledpeoplesuchassmiths,leatherworkersorcarpenters.Itwasthenthatthequestionofpaymentarose.
Atfirsthegotwhathewantedbyasimpleprocessofexchange.Thesmithwhohadnotthetimetolookafterlandorcattlewasgladtotakemeatorgrainfromthefarmerinexchangeforanaxeoraplough.Butasmoreandmoregoodswhichhadnofixedexchangevaluecameonthemarket,exchangebecametoocomplicatedtobesatisfactory.Anotherproblemarosewhenthosewhomadethingswantedtogetstocksofwoodorleather,oriron,buthadnothingtoofferinexchangeuntiltheirfinishedgoodswereready.Thusthedifficultiesofexchangeledbydegreestotheinventionofmoney.Insomecountrieseasilyhandledthingslikeseedsorshellsweregivenacertainvalueandthefarmer,insteadofpayingthesmithforanewaxebygivinghimsomemeatorgrain,gavehimsomanyshells.Ifthesmithhadanyshellsleftwhenhehadboughthisfood,hecouldgetstocksoftherawmaterialsofhistrade.Insomecountriesquitelargethingssuchascowsorcamelsorevenbigflatstoneswereusedfortrade.Later,piecesofmetal,bearingvaluesaccordingtotherarityofthemetalandthesizeofthepieces,orcoinswereused.Moneyasweknowithadarrived.
1.Exchangeofgoodsbecamedifficultbecause_________.
Amanbecamemorecivilized
Bsmithsbegantolookafterlandorcattleintheirsparetime
Cmoreandmoregoodswhichhadnofixedexchangealuescametothemarker
Dfarmershadn'tenoughgrainormeattoprovidefor
skilledworkers
2.Moneywasnotuseduntil_______.
Apaperwasinvented
Bpeoplepracticedasimpleprocessofexchange
CnothingcouldbeofferedinexchangeDtheexchangeofonethingforanotherbecametoocomplicated
3.Thebesttitleforthispassageis_____.
AWhatismoney
BWhataremoney'sfunctions.
CTheimportanceofmoney
DThebeginningofmoney
Thegoodsarepackedincartonsinterlinedwith________material.
WhatdoShona'sinitialresultsshowaboutmedicalservicesinBritain?
Theredcolorcanstimulateallour____,includingappetite.
