选择题 .  In multlpoint networks, there are tree persistence methods when a station finds a channel busy. in the 1-persistent,after the station finds the line idle. It sends its frame immediately this method has the ______chance of collsion 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.