The request that can be granted safely is **B. P5 requesting one instance of R**.
In the initial safe state, the total number of instances of R that are available is 10 - (2 + 2 + 2 + 1) = 1.
If P5 requests one instance of R, the total number of instances of R that are available will be 0.
However, P1, P2, P3, and P4 have maximum needs of 5, 7, 4, and 9 instances of R respectively. Therefore, it is possible to allocate the remaining 0 instances of R to these processes in such a manner as to satisfy their maximum needs.
Therefore, the request that can be granted safely is **B. P5 requesting one instance of R**.
The other requests cannot be granted safely because they would leave the system in an unsafe state. For example, if P1 requests one instance of R, the total number of instances of R that are available will be 1.
However, P2, P3, and P4 have maximum needs of 7, 4, and 9 instances of R respectively. Therefore, it is not possible to allocate the remaining 1 instance of R to these processes in such a manner as to satisfy their maximum needs.
As a result, the system would be in an unsafe state if P1's request was granted. The same is true for the requests of P2 and P4.