Answer:
A) The y-axis
Explanation:
One thing to notice is that the values of the y-coordinates don't change. They don't move up or down. This means that can't be reflected vertically, as would happen with C) or D). This leaves us with A and B. For each coordinate pair, the x-coordinate is made negative (for instance, (4, 2) becomes (-4, 2)). Both 4 and -4 are 4 units away from 0, which makes sense because a shape reflected over a line would maintain its distance from the line. 5 and -5 are 5 units away from 0 and 6 and -6 are 6 units away from 0. x = 0 is the y-axis, so the answer is A.