Which of the following sets represents a function?
a.
{(0, 1), (1, 2), (3, 4), (5, 6), (5, 7)}
b.
{(3, 4), (4, 4), (5, 4)}
c.
{(1, 3), (5, 2), (1, -3), (5, -2)}
d.
{(5, 8), (7, 2), (5, 10)}

The answer would be B because to have a function none of the x's can be the same, and we know that it's (x,y) so all of the first numbers are x's
In the first answer choice the x's would be 0,1,3,5,&5 but the 5 is repeated so we toss that answer choice
In answer choice B, the x's are 3,4,&5, so that's a maybe
In C, the x's are 1,5,1,&5 so we know that's not correct because the 5's and the 1's are both repeated
Last but not least, in D, the x's are 5,7,&5, the 5's are repeated so that leaves us with our answer of B. {(0,1), (1,2), (3,4), (5,6), (5,7)}