Which of the relations given by the following sets of ordered pairs is a function?

A. { (1,2), (2,3), (3,4), (2,1), (1,0) }

B. { (2,-8), (6,4), (-3,9), (2,0), (-5,3) }

C. { (1,-3), (1,-1), (1,1), (1,3), (1,5) }

D. { (-2,5), (7,5), (-4,0), (3,1), (0,-6) }

Functions cannot have the same X value (the first number), but they can have the same Y value (the second number).

A. { (1,2), (2,3), (3,4), (2,1), (1,0) }

B. { (2,-8), (6,4), (-3,9), (2,0), (-5,3) }

C. { (1,-3), (1,-1), (1,1), (1,3), (1,5) }

D. { (-2,5), (7,5), (-4,0), (3,1), (0,-6) }

Choice A. has two repeating X values [ (1,2) and (1,0), (2,3) and (2,1) ]

Choice B. has one repeating X value [ (2, - 8) and (2,0) ]

Choice C. all has a repeating X value (1)

Choice D doesn't have any repeating X values.

In short, your answer would be choice D [ { (-2,5), (7,5), (-4,0), (3,1), (0,-6) }] because it does not have any repeating X values.