8、动点作曲线运动时，“匀速运动”指的是全加速度为零。 （ ）

A）力多边形不自行封闭，则对应的平面汇交力系一定不平衡。
B）力偶在任何坐标轴上投影的代数和恒为零。
C）合力在某轴上的投影等于各分力在同一轴上投影的代数和。
D）力可以平移到刚体内的任意一点。

A. (a) Transceivers
B. (b) Terminators
C. (c) Optical Fiber
D. (d) Repeaters
E. (e) Coaxial cable

A. (a) Listen (carrier sense) before transmit.
B. (b) If channel is sensed idle, then transmit entire frame even a collision is detected.
C. (c) If channel is sensed idle, then transmit a frame and stop the transmission when a collision is detected.
D. (d) If channel is sensed busy, then defer transmission for a random time.
E. (e) If channel is sensed busy, then defer transmission until the channel is idle.