The growth of switching has (135) a new generation of network management tools that help (136) cope with the challenges, (137) them to correlate device alarms in order to (138) pinpoint root causes, or to monitor service levels without depending on IP subnet schemes. These new tools have become essential to coping with the primary (139) effect of any treatment that significantly increases network flexibility: added complexity.

138（）

A.technicians 

B.workers 

C.salesmen 

D.professors

电流是表示______的物理量，用符号______表示．电流的国际单位是______，符号______，电流还有其他单位是______、______．

（1）房间灯泡中的电流约0.2A．等于______mA．

（2）半导体收音机电源的电流约50mA等于______A．

（3）计算器中电源的电流约100μA，等于______A，

（4）家用冰箱的电流约1A，等于______mA．