单选题：Suppose we have four resources, RA, RB, RC and RD. Given below a

Suppose we have four resources, RA, RB, RC and RD. Given below allocation matrix, available vector and maximal requirement matrix.
```
Max
RA RB RC RD
P0 3 2 1 4
P1 0 2 5 2
P2 5 1 0 5
P3 1 5 3 0
P4 3 0 3 3

Allocation
RA RB RC RD
P0 1 0 1 1
P1 0 1 2 1
P2 4 0 0 3
P3 1 2 1 0
P4 1 0 3 0

Available
RA RB RC RD
1 2 2 2
```
What is the current state of existing system?@[C](1)
A. deadlock
B. unsafe
C. safe
D. not sure




A.deadlock
B.unsafe
C.safe
D.not sure


答案：C