The indicator light of OptiXtrans E6600 LOSn is red and blinks once every 3 seconds. Which of the following is it?

The indicator light of OptiXtrans E6600 LOSn is red and blinks once every 3 seconds. Which of the following is it?
A . The optical port of the single board reports the R_LOS alarm
B. The optical port of the single board reports the MS_RDI alarm
C. The board is not in place
D. The optical module is not in place

Answer: B