Answer: A
Explanation:
It will never be a function if an x-value repeats. This data set thus represents a function.
With that in mind, we can use process of elimination to find the answer
We can immediately eliminate C because it is simply not true. You can tell by just looking at the data table that this is the case.
We know that it is a function so B is not correct. This also eliminates D as the vertical line test is used to see if an x-value repeats.
We are left with A, which is reasonable as the x-value is never shown to repeat.
Have a good one :D