单项选择题
A. 0
B. 1
C. 2
D. 3
E. 5
多项选择题 Whataretwocharacteristicsofdual-ringinterconnectinSDHnetworks？（）
单项选择题 A customer would like to create a 1：1 protection group with a DS3Ni-12 card. Where should it be placed in the chassis？（）
单项选择题 A customer has 20 E1s to add between far-end nodes in an SNCP ring. What type of circuit would you recommend？（）