What set of reflections would carry triangle ABC onto itself?

The correct answer is y-axis, x-axis, y-axis, x-axis. The y-axis is the vertical line, and the x-axis is the horizontal line. If the triangle is in the upper right quadrant, and is reflected first over the y-axis, it will be in the upper left quadrant. Then, when the triangle is reflected again over the x-axis, it will be in the lower left quadrant, diagonal to the initial triangle. When the triangle is again reflected over the y-axis, it will be in the lower right quadrant, below the initial triangle. Finally, when the triangle is reflected over the x-axis, it will be on top of the original triangle in the upper right quadrant.