Link Utilization = efficiency = Useful Time / Total Time
Transmission Time = L / B = ($2^{10}$ * 8) / (1.5 *$10^{6}$) = 5.46*$10^{-3}$ s
Propogation Time = RTT/2 = 45*$10^{-3}$ / 2 = 22.5*$10^{-3}$ s
Useful Time = Transmission Time
Total Time = Transmission Time + Propogation Time + Propogation Time(ACK)
= 5.46 * $10^{-3}$ + 45*$10^{-3}$ = 50.46*$10^{-3}$ s
Link Utilization = efficiency = Useful Time / Total Time = 5.46*$10^{-3}$ / 50.46*$10^{-3}$ = 0.108
but, as you can see that no option matches .
This question is not clear or ambiguous . i think they forget to mention that RTT = Transmission Time + 2*Propogation Time
but in almost all cases we assume that RTT = ransmission Time + Propogation Time
Let's assume RTT = Transmission Time + 2*Propogation Time
then , Link Utilization = Transmission Time / RTT // here total time is itself RTT
Link Utilization = 5.46*$10^{-3}$ / 45*$10^{-3}$ = 0.121
but again this question is not proper . Gate will not ask you this type of question . data given in gate will always proper