A. ESF
B. PRS
C. DUS
D. SMC
E. B8ZS

A. J0 errors detected in a specified interval
B. errors detected in a given Errored Second (ES)
C. errors detected in a given Severely Errored Second (SES)
D. errors the encryption algorithm detects in a specified interval
E. Bit Interleaved Parity (BIP) errors detected in a specified interval

A. prevent the leakage of external fiber emissions
B. provide the optical network with the highest level of security possible
C. assure an even distribution of 1's and 0's for extended transmitter life
D. assure an adequate number of transitions for clock recovery at the receiver
E. prevent the receiver from assuming AIS inadvertently when all 0's are received

A. fibers are terminated incorrectly on a node
B. the channel number in the received K1 byte is not identical to the channel number transmitted in the K2 byte
C. the channel number in the received C1 byte is not identical to the channel number transmitted in the C2 byte
D. the channel number in the received C2 byte is not identical to the channel number transmitted in the C1 byte
E. the channel number in the received K2 byte is not identical to the channel number transmitted in the K1 byte

A.255
B.512
C.1024
D.4096

A.line timing
B.loop timing
C.internal timing
D.through timing
E.external timing

A.2
B.3
C.4
D.20
E.22
F.24

A. VT circuits
B. STS circuits
C. VT tunnel circuits
D. 1:1 protection circuits
E. 1:N protection circuits

A.2；0
B.3；2
C.3；5
D.4；0
E.6；0
F.6；2

A. Slot 2 and Slot 4
B. Slot 4 and Slot 6
C. Slots 5 or 13 only
D. Slot 16 and Slot 17

A.1+0
B.1+1
C.1：1
D.1：N