● In multipoint networks , there are tree persistence methods when a station finds a channel busy.in the 1-persistent method,after the station finds the line idle,it sends its frame immediately.this method has the （  ） chance of collision because two or more stations may find the line （  ） and send their frames immediately. In the nonpersistent method , a station that has a frame to send （  ） the line . If the line is idle , it sends immediately If the line is not idle , it waits a （  ） amount of time and then senses the line again.The nonpersistent approach （  ） the chance of collision because it is unlikely that two or more stations will wait the same amount of time and retry to send simultaneously The p-persistent approach combines the advantages of the other two strategies . It reduces the chance of collision and improves efficiency.

（71）A．the lowest

B.the highest

C.possible

D.no

（72）A．idle

B.busy

C.useful

D.unusable

（73）A．overhears

B.hears

C.listens

D.senses

（74）A．random

B.big

C.medium

D.small

（75）A．increases

B.equalizes

C.reduces

D.cancels

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