Answer B
The system uses Round robin algorithm of time quantum = 4ms
| o A |4 B |8 C |12 D | 16 A |20 C|24| D |25 C |26
average turn around time = (Finished time- start time) of each process/ no of processes.
=(20-0)+(8-1)+(26-2)+(25-3) /4 = 18.25 ms