单项选择题
A. 10 B. 32 C. 64 D. 84 E. 96
WhichtimingmodeismostappropriateforanONS15454thathaslos...
单项选择题Which timing mode is most appropriate for an ONS 15454 that has lost its BITS-1 and optical references？（）
A. line timing B. loop timing C. internal timing D. through timing E. external timing
