Inmultipointnetworks,therearetreepersistencemethodswhenastationfindsachannelbusy.inthe1-persistentmethod,afterthestationfindsthelineidle,itsendsitsframeimmediately.thismethodhasthe()chanceofcollisionbecausetwoormorestationsmayfindtheline(请作答此空)andsendtheirframesimmediately.Inthenonpersistentmethod,astationthathasaframetosend()theline.Ifthelineisidle,itsendsimmediatelyIfthelineisnotidle,itwaitsa()amountoftimeandthensensesthelineagain.Thenonpersistentapproach()thechanceofcollisionbecauseitisunlikelythattwoormorestationswillwaitthesameamountoftimeandretrytosendsimultaneouslyThep-persistentapproachcombinestheadvantagesoftheothertwostrategies.Itreducesthechanceofcollisionandimprovesefficiency.
A.idle B.busy C.useful D.unusable正确答案A