Answer:
D.
Step-by-step explanation:
The easiest way to tell is a relation is a function is to look at every x. A function cannot have two x's that are the same.
A. There are two x's with the value of 10.
B. There are two x's with the value of 20.
C. If you wrote this in ordered pairs, there would be two x's with the value 2.
D. Every x is different, so the answer is D.
Hope this helps! Have a great day c:
