Answer:
b. is the only set of points that is a function.
Step-by-step explanation:
A relation is a function is there is not more than one y assigned to a x.
A relation relates a variable to another variable. Option a does not not this.
A set of points is a relation. A trick to figuring out if is a function is to see if all x's are different.
Let's look at b. All the x's are different there so it is a function.
Now c, we see that there are two different points with the same x so this is not a function.
Now d, we see that there are two different points with the same x so this is not a function.
