To identify a line of reflection that flips the polygon onto itself, you typically look for lines that create symmetrical halves of the polygon.
If the polygon is symmetrical concerning the x-axis, the line of reflection could be \( y = 0 \). Similarly, if the polygon is symmetrical about the y-axis or some vertical/horizontal line through its center, you would choose that corresponding line.
Based on the responses you provided, if you can determine that the polygon is symmetrical about the x-axis, then the correct line of reflection would be \( y = 0 \).
If you need a more specific answer based on the image, it is essential to visualize or analyze the symmetry of the polygon itself. Assuming a standard case based on your options, the most generic answer would be:
y = 0