Which of the following is an example of spooled device?

Four jobs to be executed on a single processor system arrive at time $${0^ + }$$ in the order $$A, B, C, D.$$ their burst $$CPU$$ time requirements are $$4, 1, 8, 1$$ time units respectively. The completion time of A under round robin scheduling with time slice of one time units.

A critical section is a program segment

A solution to the Dining Philosophers Problem which avoids deadlock is