Which transformation flips a figure over a mirror or reflection line?

• A. Reflection
• B. Rotation
• C. Intersect
• D. Vertex

Answer: (A)

Flipping a figure over a line is reflection. A line of reflection acts like a mirror, so every point of the shape has a partner on the opposite side at the same distance from that line, and the line itself stays in place. The segment joining a point and its image is perpendicular to the line and is cut in half by the line. This is what creates a mirror image of the figure. Other ideas described by the other terms don’t involve flipping over a line: rotation spins the figure around a point, not across a line; intersect and vertex refer to lines crossing or a corner point, not a flipping action. So the flip-over-the-line transformation is reflection.