Which of the relations given by the following sets of ordered pairs is a function?
(8,1),(-4,1),(3,5),(0,4),(-1,2)
{(-5,-4),(-4,-3),(-3,-2),(-4,-5),{(-2,-1)}}
((2,4),(2,6),(2,8),(2,10),(2,12)]
({(0,3),(-6,8),(-3,5),(0,-3),(7,11)})