stop-and-wait

go-back-n

selective-reject

both (a) and (b)

Does not require global time synchronization

does require global time synchronization

both (a) and (b)

none of these

non-return to zero code

polar code

both 1)non-return to zero code and 2)polar code

none of these

TDMA

stop and wait

continuous ARQ

none of these

within each user session

with each user session

at system generation time only

none of these