请简述SDH体制中怎样实现不同级别信号层层监控的,以及不同级别,信号是通过什么在帧结构中定位的。
参考答案:
通过各级开销来监控,通过AU-PTR,TU-PTR来定位的。
— How will she deal with the work?
— She doesn't want to do it by herself. She wants to ask someone else to do it, . [ ]
A. yet
B. instead
C. too
D. either
国家财政收入来源中,占主导地位的是______。