CSMA, although more efficient than ALOHA or slotted ALOHA, still has one glaring inefficiency. If the medium is busy, the station will wait for a random amount of time. When two frames collide, the medium remains （ ） for the duration of transmission of both damaged frames. The use of random delays reduces the probability of（ ）. For（ ）frames, compared to propagation time, the amount of wasted capacity can be considerable. This waste can be reduced if a station continues to listen to the medium while（ ）.
The maximum utilization depends on the length of the frame and on the（请作答此空） time; the longer the frames or the shorter the propagation time，the higher the utilization.
