The correct answer would be choice "C" because first off, you can see that the shape hasn't grown/shrink. We can also see that it doesn't seemed to have rotated, otherwise it would be flipped in a certain direction. So, now we're left with a reflection over the y-axis/reflection over x-axis.
If the shape had reflected over the x-axis, it would be in the lower quadrants of the graph, since it would be flipped over a horizontal line. But instead, the shape has flipped to the left, making it a reflection over the y-axis.
