An intErnEt is A ComBinAtion oF nEtworks ConnECtED By (26) ．whEn A DAtAgrAm goEs From A sourCE to A (27) ，it will proBABly pAss mAny (28) until it rEAChEs thE routEr AttAChED to thE DEstinAtion nEtwork．
A、routEr rECEivEs A (29) From A nEtwork AnD pAssEs it to AnothEr nEtwork．
A、routEr is usuAlly AttAChED to sEvErAl nEtworks．whEn it rECEivEs A pACkEt，to whiCh nEtwork shoulD it pAss thE pACkEt thE DECision is BAsED on optimizAtion：whiCh oF thE AvAilABlE (30) is thE optimum pAthwAy
A、pAthwAys B．routErs
C、DiAgrAms
D、CAlls