A relation from P to Q is
A universal set of P × Q
P × Q
An equivalent set of P × Q
A subset of P × Q
A relation from P to Q is a subset of P × Q.
Let A = {1,2,3,4} and B = { x,y,z}. Then R = {(1,x) , ( 2,z), (1,y), (3,x)} is