Answer:
A
Step-by-step explanation:
In a function, each x value must have a singular y value. This means that one x-value (the values on the left) may not have a line pointing to 2 different y-values (the values on the right). In the first relation, the x-value of 6 points to both 4 and 6. This means that the value repeats, and in a function x-values cannot repeat.
However, y-values can repeat. So, situations like that seen in D, where both the x-values of 2 and 4 equal the y-value of 6 are fine.
