Value for which system never enters into deadlock is | UGC NET

UGC NET 2018: 

Suppose a system has 12 instances of some resources with n processes competing for that resource. Each process may require 4 instances of the resource. The maximum value of n for which the system never enters into deadlock is
A) 3
B) 4
C) 5
D) 6
Solution:
No. of instances = 12
Number of process is n.
Each process required 4 instance.
Lets, 
Divide 12 instances into set of 4.
Set1 = 4
Set2 = 4
Set3 = 4
Set1+Set2+Set3 = 12
Now allocate each set to a process.
Process P1 = Set1
Process P2 = Set2
Process P3 = Set3
No other instance available for any next process.
So, the maximum value of n for which the system never enters into deadlock is 3.