Identify the relation that is also a function.

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

B. { (1, 0) (2, 3) (3, - 1) (1, 5) }

C. { (4, 2) (4, - 3) (9, 3) (9, - 3) }

D. { (5, 4) (5, 1) (5, 3) (0, 5) }

A is a function; B, C and D are not.

Step-by-step explanation:

In other words: Identify the sole function among these relationships.

A function maps any input onto exactly one output.

If a relationship maps any input onto more than one output, it is not a function.

Thus, we eliminate B, C and D. In B, for example, we have the inputs {1, 2, 3}, where the '1' has two y-values associated with it.

On the other hand, A has the domain {-1, 0, 1, 2}, and all four inputs have exactly one associated output.