Answer:
D
Explanation:
In order for a line on a graph to be a function it has to pass the vertical line test.
How you do that for points, multiple X values can't have more than 1 Y value.
A has points (2, -6) and (2, 6), so it doesn't pass the vertical line test because the X value (2) goes to multiple Y values (6 and -6).
B has points (-3, -5) and (-3, -4), so it doesn't pass the vertical line test because the X value (-3) goes to multiple Y values (-3 and -4)
C has points (-8, 9) and (-8, 4), so it doesn't pass the vertical line test because the X value (-8) goes to multiple Y values (4 and 9).
C also has the points (8, -5) and (8, 1), and this has the same problem as all of the other problems.
D has {(-3, 5), (6, 10), (5, 2) , (-6, -5), and (3, 9)} which every X value has exactly 1 Y value.
Therefore, D is the correct answer.