同步链路的长度应越短越好，两个G．812时钟之间的SDH设备时钟数不宜超过（）个。
A.20个
B.30个
C.40个
D.60个
参考答案：A
3（x﹣2）+x2﹣2x=0
-My prize is different from .
-But is the same as mine. [ ]
A. Dick；yours
B. Dick；your
C. Dick’s；your
D. Dick’s; yours
