Answer:
B
Explanation:
Fortunately we do not need D. The answer of the three that we can see is B.
Every x value except one has 2 y values and that means the vertical line test will not work and that is how a function is defined by there being 1 y for a bunch of xs. This is one of those questions where 1 of 2 opposite answers must be correct. The vertical line test is meant to weed out any 2 ys belonging to 1 x and that is how a function is defined.
It would be nice to know what D said. You should add a comment.
Thank you for putting D up. There is only 1 point that has 1 x value and 1 y value. That is the "vertex." Otherwise every other pair of y values (1 plus and the other minus) have 1 x value. That means that the vertical line test fails.