Let a system allocate resources to processes as long as the system state remains safe with respect to deadlocks. Note that a system state is safe if there is a way to allocate the remaining resources in such a manner as to satisfy the maximum needs of all the processes. With respect to a resource R, let the system have 10 instances of the resource and let there be five processes P1, P2, P3, P4 and P5 that have maximum needs of 5, 7, 4, 9 and 8 instances of the resource respectively.
Start with a safe state in which P1 is holding no instances, P2, P3 and P4 are holding two instances each and P5 is holding one instance of R. Now, consider each of the following requests. For each request, determine if it can be granted while keeping the system in a safe state. Identify the request that can be granted safely.
A. P1 requesting one instance of R
B. P5 requesting one instance of R
C. P2 requesting two instances of R
D. P4 requesting one instance of R