On an ONS 1545
题目
On an ONS 15454 node you can tunnel a（n） （）.
- A、 SDH circuit over a SONET network delivering it as an SDH signal
- B、 SDH circuit over a SONET network delivering it as a SONET signal
- C、 SONET circuit over an SDH network delivering it as an SDH signal
- D、 SONET circuit over an SDH network delivering it as a SONET signal
