Suppose a system contains $n$ processes and system uses the round-robin algorithm for CPU scheduling then which data structure is best suited ready queue of the process
Circular queue is the best data structure for round-robin CPU scheduling algorithm .
In round-robin CPU scheduling if the timer goes off first, then the process is swapped out of the CPU and moved to the back end of the ready queue.
The ready queue is maintained as a circular queue, so when all processes have had a turn, then the scheduler gives the first process another turn, and so on.
So option C is correct.
I'm no expert, but I can answer your question with some confidence.
For FCFS scheduling, FIFO queue is used.
For SJF (non-preemptive) and priority, a priority queue (min-heap) is used.