Click the Exhibit button. A customer has several interconnected core rings (see exhibit). They want to create several irtual rings?utilizing their OC-192 backbone (nodes 1,2,3,4). What should you recommend?（）

A. PPMN with BLSR rings
B. PPMN with UPSR rings
C. 1:N protection on all core circuits
D. multi-ring interconnect with BLSR rings