ACCorDing to thE Fourth pArAgrAph, onE DisADvAntAgE oF AlliAnCEs ForEsEEn By thE CritiCs is thAt Air trAvEl mAy BE morE ExpEnsivE As A rEsult oF ______.
A．lEss ConvEniEnCE
B．highEr opErAtion Costs
C．lEss CompEtition
D．morE joint mArkEting