1NE1 is interconnected with NE2. NE1 uses OptiX SDH equipment and uses a VC4:1:2 timeslot. If the service can be opened normally, what is the VC12 timeslot number that the other end needs to use when using equipment from other manufacturers?

1NE1 is interconnected with NE2. NE1 uses OptiX SDH equipment and uses a VC4:1:2 timeslot. If the service can be opened normally, what is the VC12 timeslot number that the other end needs to use when using equipment from other manufacturers?
A . 2-1-1
B . 1_2_1
C . 1_1_2
D . 2_2_1

Answer: A