If both the bidirectional OA and OSC report a loss of light alarm in a WDM network, which is the most likely cause?

If both the bidirectional OA and OSC report a loss of light alarm in a WDM network, which is the most likely cause?
A . One-way interruption of line optical fiber
B . The line optical fiber is interrupted in both directions
C . Unidirectional degradation of line fiber
D . Bidirectional degradation of line optical fiber

Answer: B